The effect of insufficient quadriceps strength on gait after anterior cruciate ligament reconstruction

Rehabilitation-Specific Predictors of Pain Intensity and Physical Activity Levels in Individuals With Acetabular Dysplasia 6 Months After Periacetabular Osteotomy

INTRODUCTION

Individuals with acetabular dysplasia often report hip joint instability, pain, and poor hip-related function. Periacetabular osteotomy (PAO) is a surgical procedure that aims to reposition the acetabulum to improve joint congruency and improve pain and function. We aimed to examine the influence of presurgery clinical measures on functional recovery following PAO and the associations among clinical outcomes after PAO.

METHODS

We screened 49 potential participants, 28 were enrolled, and 23 completed both study visits (pre-PAO and 6 months post-PAO). We evaluated dynamometer-measured hip and thigh strength, loading patterns during a squat and countermovement jump (CMJ), pain intensity, and device-measured physical activity (PA) levels (light, moderate-to-vigorous PA [MVPA], and daily steps). We used linear regression models to examine the influence of muscle strength (peak torque; limb symmetry index [LSI]) and loading patterns before PAO on pain intensity and PA levels in individuals 6 months following PAO. Additionally, we used Pearson correlation coefficient to examine cross-sectional associations among all variables 6 months following PAO.

RESULTS

Lower extremity muscle strength and loading patterns during the squat and CMJ before PAO did not predict pain intensity or device-measured PA levels in individuals 6 months following PAO (p > 0.05). Six months following PAO, higher knee extensor LSI was associated with higher time spent in MVPA (r = 0.56; p = 0.016), higher hip abductor LSI was associated with both lower pain (r = 0.50; p = 0.036) and higher involved limb loading during the squat task (r = 0.59; p = 0.010). Lastly, higher hip flexor LSI was associated with higher CMJ takeoff involved limb loading (r = 0.52; p = 0.021) and higher involved hip extensor strength was associated with higher CMJ landing involved limb loading (r = 0.56; p = 0.012).

CONCLUSION

Six months after PAO, higher hip and thigh muscle strength and strength symmetry were associated with lower pain, higher PA levels, and greater normalized limb loading during dynamic movement tasks.

Quadriceps Activation After Anterior Cruciate Ligament Reconstruction: The Early Bird Gets the Worm!

Arthrogenic Muscle Inhibition (AMI) is a phenomenon observed in individuals with joint injury or pathology, characterized by a reflexive inhibition of surrounding musculature, altered neuromuscular control, and compromised functional performance. After anterior cruciate ligament reconstruction (ACLR) one of the most obvious consequences of AMI is the lack of quadriceps activation and strength. Understanding the underlying mechanisms of AMI is crucial for developing effective therapeutic interventions. The surgical procedure needed to reconstruct the ACL has biochemical et physiological consequences such as inflammation, pain, and altered proprioception. These alterations contribute to the development of AMI. Therapeutic interventions aimed at addressing AMI encompass a multidimensional approach targeting pain reduction, inflammation management, proprioceptive training, and quadriceps activation. Early management focusing on pain modulation through modalities like ice, compression, and pharmacological agents help mitigate the inflammatory response and alleviate pain, thereby reducing the reflexive inhibition of quadriceps. Quadriceps activation techniques such as neuromuscular electrical stimulation (NMES) and biofeedback training aid in overcoming muscle inhibition and restoring muscle strength. NMES elicits muscle contractions through electrical stimulation, bypassing the inhibitory mechanisms associated with AMI, thus facilitating muscle activation and strength gains. Comprehensive rehabilitation programs tailored to individual needs and stage of recovery are essential for optimizing outcomes in AMI. The objective of this clinical viewpoint is to delineate the significance of adopting a multimodal approach for the effective management of AMI, emphasizing the integration of pain modulation, proprioceptive training, muscle activation techniques, and manual therapy interventions. Highlighting the critical role of early intervention and targeted rehabilitation programs, this article aims to underscore their importance in restoring optimal function and mitigating long-term complications associated with AMI.

Effect of Running Speed on Knee Biomechanics in Collegiate Athletes Following Anterior Cruciate Ligament Reconstruction

INTRODUCTION

Athletes after anterior cruciate ligament reconstruction (ACLR) demonstrate altered surgical knee running kinematics and kinetics compared with the nonsurgical limb and healthy controls. The effect of running speed on biomechanics has not been formally assessed in athletes post-ACLR. The purpose of this study was to characterize how knee biomechanics change with running speed between 3.5-7 (EARLY) and 8-13 (LATE) months post-ACLR.

METHODS

Fifty-five Division I collegiate athletes post-ACLR completed running analyses (EARLY: n = 40, LATE: n = 41, both: n = 26) at 2.68, 2.95, 3.35, 3.80, and 4.47 m·s -1 . Linear mixed-effects models assessed the influence of limb, speed, time post-ACLR, and their interactions on knee kinematics and kinetics.

RESULTS

A significant limb-speed interaction was detected for peak knee flexion, knee flexion excursion, and rate of knee extensor moment ( P < 0.02), controlling for time. From 3.35 to 4.47 m·s -1 , knee flexion excursion decreased by -2.3° (95% confidence interval, -3.6 to -1.0) in the nonsurgical limb and -1.0° (95% confidence interval, -2.3 to -0.3) in the surgical limb. Peak vertical ground reaction force, peak knee extensor moment, and knee negative work increased similarly with speed for both limbs ( P < 0.002). A significant limb-time interaction was detected for all variables ( P < 0.001). Accounting for running speed, improvements in all surgical limb biomechanics were observed from EARLY to LATE ( P < 0.001), except for knee flexion at initial contact ( P = 0.12), but between-limb differences remained ( P < 0.001).

CONCLUSIONS

Surgical and nonsurgical knee biomechanics increase similarly with speed in collegiate athletes at EARLY and LATE, with the exception of peak knee flexion, knee flexion excursion, and rate of knee extensor moment. Surgical knee biomechanics improved from EARLY and LATE, but significant between-limb differences persisted.

The Influence of Knee Position on Ultrasound Imaging of Femoral Cartilage in Individuals with Anterior Cruciate Ligament Reconstruction

BACKGROUND

Articular cartilage is important for knee function and can be imaged using ultrasound. The purpose was to compare femoral cartilage thickness and echo intensity (EI) measured at 90° and 140° of knee flexion and between limbs in a cohort with unilateral anterior cruciate ligament reconstruction (ACLR). We also examined associations between gait biomechanics and cartilage outcomes.

METHODS

Twenty-seven individuals with primary unilateral ACLR participated (12 men, 15 women; age = 22.3 ± 3.8 years; time since ACLR = 71.2 ± 47.2 months). Ultrasound was used to obtain femoral cartilage measurements. Gait outcomes included peak KFA (knee flexion angle) and peak external knee flexion moment (KFM). Cartilage outcomes were compared using a 2 (position) × 2 (limb) repeated measures ANOVA (analysis of variance). Gait and cartilage associations were assessed using linear regression.

FINDINGS

There were no position × limb interactions for any cartilage outcome (all P > 0.05). Medial (P = 0.038) and central cartilage (P < 0.001) were thicker, whereas central (P = 0.029) and lateral cartilage EI (P = 0.003) were lower when measured at 90° than those at 140° of knee flexion. Medial cartilage was thicker in the ACLR than that in the contralateral limb (P = 0.016). A larger KFM was associated with thicker medial cartilage (ΔR2 = 0.146, P = 0.021) and central cartilage (ΔR2 = 0.159, P = 0.039) measured at 140° of knee flexion in the ACLR limb but not at 90°.

INTERPRETATION

Findings suggest that imaging position influences cartilage thickness and EI measurements in individuals with ACLR and should be considered in study designs and clinical evaluation. A greater KFM was associated with thicker cartilage within specific portions of the distal femur.

Does It Matter? Isometric or Isokinetic Assessment of Quadriceps Strength Symmetry 9 Months After ACLR in Collegiate Athletes

BACKGROUND

Greater quadriceps strength symmetry is associated with better outcomes after anterior cruciate ligament reconstruction (ACLR). Isometric and isokinetic assessments of quadriceps strength inform therapeutic exercise prescription and return-to-sport decisions. It is unclear whether isometric and isokinetic measures provide similar information post-ACLR.

HYPOTHESIS

Quadriceps strength symmetry is similar between isometric and isokinetic assessments. Isokinetic and isometric strength symmetries have similar associations to functional knee kinetics and self-reported knee function.

STUDY DESIGN

Cross-sectional study.

LEVEL OF EVIDENCE

Level 3.

METHODS

NCAA Division I athletes (N = 35), 8.9 ± 2.5 months post-ACLR completed isometric and isokinetic quadriceps strength assessments, countermovement jumps (CMJs), and treadmill running. Self-reported knee function was assessed using the International Knee Documentation Committee Subjective Knee Form (IKDC). Agreement between isometric and isokinetic strength symmetry was assessed using Bland-Altman analysis, with associations to functional knee kinetics and IKDC assessed using Pearson correlations and linear regressions.

RESULTS

Mean difference in quadriceps strength symmetry between isokinetic and isometric assessments was 1.0% (95% limits of agreement of -25.1% to 23.0%). Functional knee kinetics during running and CMJ were moderately to strongly associated with isometric strength symmetry (r = 0.64-0.80, P < 0.01) and moderately associated with isokinetic strength symmetry (r = 0.41-0.58, P < 0.01). IKDC scores were weakly to moderately associated with isometric (r = 0.39, P = 0.02) and isokinetic (r = 0.49, P < 0.01) strength symmetry.

CONCLUSION

Isokinetic and isometric assessments of quadriceps strength symmetry in collegiate athletes 9 months post-ACLR demonstrated strong agreement. Quadriceps strength symmetry is associated with functional knee kinetic symmetry post-ACLR.

CLINICAL RELEVANCE

Considerable individual variation suggests mode of contraction should be consistent throughout postoperative assessment. Isometric strength symmetry may be a better indicator of functional knee kinetic symmetry, while isokinetic strength symmetry may be associated more closely with patient-reported outcomes.

Longitudinal Changes in Quadriceps Morphology over the First 3 Months after Anterior Cruciate Ligament Reconstruction

PURPOSE

Neuromuscular deficits and atrophy after anterior cruciate ligament reconstruction (ACLR) may be accompanied by changes in muscle composition and poor quadriceps muscle quality (QMQ). Quadriceps atrophy occurs after ACLR but improves within the first three postoperative months, yet this hypertrophy could be attributable to increases in noncontractile tissue (i.e., poor QMQ). The purposes of this study were to evaluate changes in QMQ after ACLR and to determine if changes in QMQ and cross-sectional area (CSA) occur in parallel or independently.

METHODS

A longitudinal prospective cohort design was implemented to evaluate QMQ and CSA in 20 individuals with ACLR and 12 healthy controls. Participants completed three testing sessions (baseline/presurgery, 1 month, and 3 months) during which ultrasound images were obtained from the vastus lateralis (VL) and rectus femoris (RF). QMQ was calculated as the echo intensity (EI) of each image, with high EI representing poorer QMQ. Anatomical CSA was also obtained from each image.

RESULTS

RF and VL EI were greater at 1 and 3 months in the ACLR limb compared with baseline and the contralateral limb and did not change between 1 and 3 months. VL and RF CSA in the ACLR limb were smaller at 1 and 3 months compared with the contralateral limb and controls (VL only) but increased from 1 to 3 months. Changes in QMQ and CSA were not correlated.

CONCLUSIONS

QMQ declines within the first month after ACLR and does not improve by 3 months although hypertrophy occurs, suggesting that these morphological characteristics change independently after ACLR. Poorer QMQ represents greater concentration of noncontractile tissues within the muscle and potentially contributes to chronic quadriceps dysfunction observed after ACLR.

Quadriceps composition and function influence downhill gait biomechanics >1 year following anterior cruciate ligament reconstruction

BACKGROUND

Quadriceps dysfunction is common following anterior cruciate ligament reconstruction and contributes to aberrant gait biomechanics. Changes in quadriceps composition also occur in these patients including greater concentrations of non-contractile tissue. The purpose of this study was to evaluate associations between quadriceps composition, function, and gait biomechanics in individuals with anterior cruciate ligament reconstruction.

METHODS

Forty-eight volunteers with anterior cruciate ligament reconstruction completed gait biomechanics and quadriceps function and composition assessments. Gait biomechanics were sampled during downhill walking (-10° slope) on an instrumented treadmill. Quadriceps function (peak torque and rate of torque development) was assessed via maximal isometric contractions, while composition was evaluated via ultrasound echo intensity.

FINDINGS

Greater quadriceps peak torque was associated with a greater peak knee extension moment (r = 0.365, p = 0.015). Greater vastus lateralis echo intensity (i.e. poorer muscle quality) was associated with less knee flexion displacement (r = -0.316, p = 0.032). Greater echo intensity of the vastus lateralis (r = -0.298, p = 0.044) and rectus femoris (r = -0.322, p = 0.029) was associated with a more abducted knee angle at heel strike. Quadriceps peak torque explained 11-16% of the variance in echo intensity.

INTERPRETATION

Both quadriceps function and composition influence aberrant gait biomechanics following anterior cruciate ligament reconstruction. Quadriceps composition appears to provide insight into quadriceps dysfunction independent of muscle strength, as they associated with different gait biomechanics outcomes and shared minimal variance. Future research is necessary to determine the influence of changes in quadriceps composition on joint health outcomes.

Knee extension deficit during gait and knee extensor weakness persisting after saucerization and repair of discoid lateral meniscus tears

BACKGROUND

Physical function and knee kinematics recovery after discoid lateral meniscus (DLM) tear surgery are essential for a better prognosis. However, these alterations remain unclear. Therefore, this study aimed to investigate changes in physical function and knee kinematics following saucerization and DLM tear repair.

METHODS

We enrolled 16 patients who underwent saucerization and DLM tear repair. Postoperative changes in knee kinematics during gait, and physical function, were evaluated at 3, 6, and 12 months.

RESULTS

The peak flexion angle of the operated limb during weight acceptance was significantly higher than that of the contralateral limb at 3 (operated limb: 34.6 ± 8.9°, contralateral limb: 23.7 ± 8.3°; P < 0.01) and 6 months (operated limb: 32.1 ± 9.7°, contralateral limb: 24.6 ± 8.2°; P = 0.03) postoperatively, but not at 12 months (operated limb: 27.1 ± 7.1°, contralateral limb: 23.1 ± 9.5°; P = 0.22) postoperatively. The knee extensor strength of the operated limb was significantly lower than that of the contralateral limb at 3 (operated limb: 1.00 ± 0.59 Nm/kg, contralateral limb: 1.37 ± 0.59 Nm/kg; P = 0.01), 6 (operated limb: 1.22 ± 0.55 Nm/kg, contralateral limb: 1.48 ± 0.60 Nm/kg; P < 0.01), and 12 months (operated limb: 1.39 ± 0.57 Nm/kg, contralateral limb: 1.55 ± 0.64 Nm/kg; P = 0.04) postoperatively.

CONCLUSION

Knee extension deficits and extensor weakness persisted at 6 months after saucerization and repair of DLM tears. Postoperative rehabilitation should be focused on knee extension function.

Overexpression of manganese superoxide dismutase mitigates ACL injury-induced muscle atrophy, weakness and oxidative damage

Oxidative stress has been implicated in the etiology of skeletal muscle weakness following joint injury. We investigated longitudinal patient muscle samples following knee injury (anterior cruciate ligament tear). Following injury, transcriptomic analysis revealed downregulation of mitochondrial metabolism-related gene networks, which were supported by reduced mitochondrial respiratory flux rates. Additionally, enrichment of reactive oxygen species (ROS)-related pathways were upregulated in muscle following knee injury, and further investigation unveiled marked oxidative damage in a progressive manner following injury and surgical reconstruction. We then investigated whether antioxidant protection is effective in preventing muscle atrophy and weakness after knee injury in mice that overexpress Mn-superoxide dismutase (MnSOD+/-). MnSOD+/- mice showed attenuated oxidative damage, atrophy, and muscle weakness compared to wild type littermate controls following ACL transection surgery. Taken together, our results indicate that ROS-related damage is a causative mechanism of muscle dysfunction after knee injury, and that mitochondrial antioxidant protection may hold promise as a therapeutic target to prevent weakness and development of disability.

Strength symmetry after autograft anterior cruciate ligament reconstruction

OBJECTIVE

To compare postoperative isometric quadriceps strength indices (QI%) and hamstring strength limb symmetry indices (HI%) between partial thickness quadriceps tendon (pQT), full thickness quadriceps tendon (fQT), and bone-patellar-tendon bone (BPTB) autograft anterior cruciate ligament reconstruction (ACLR).

METHODS

Patients with primary ACLR with pQT, fQT, or BPTB autograft with the documentation of quantitative postoperative strength assessments between 2016 and 2021 were included. Isometric Biodex data, including QI% and HI% (calculated as the percentage of involved to uninvolved limb strength) were collected between 5 and 8 months and between 9 and 15 months postoperatively.

RESULTS

In total, 124 and 51 patients had 5-8- and 9-15-month follow-up strength data, respectively. No significant difference was detected between groups for sex. However, patients undergoing fQT were found to be older than those undergoing BPTB (24.6±7 vs 20.2±5; ​p = 0.01). There were no significant differences in the number of concomitant meniscus repairs between the groups (pQT vs. fQT vs. BPTB). No significant differences were detected in median (min-max) QI% between pQT, fQT, and BPTB 5-8 months [87 ​% (44%-130 ​%), 84 ​% (44%-110 ​%), 82 ​% (37%-110 ​%) or 9-15 months [89 ​% (50%-110 ​%), 89 ​% (67%-110 ​%), and 90 ​% (74%-140 ​%)] postoperatively. Similarly, no differences were detected in median HI% between the groups 5-8 months or 9-15 months postoperatively.

CONCLUSION

The study was unable to detect differences in the recovery of quadriceps strength between patients undergoing ACLR with pQT, fQT, and BPTB autografts at 5-8 months and 9-15-months postoperatively.

LEVEL OF EVIDENCE

III.

Joint contributions to sagittal plane total support moment in patients with knee osteoarthritis after anterior cruciate ligament reconstruction

BACKGROUND

Patients with anterior cruciate ligament reconstruction (ACLR) demonstrate lower knee loading. This study aimed to determine whether sagittal plane TSM and joint contributions to total support moment (TSM) in the surgical limb are different between athletes who did and did not show radiological features of knee OA at 2 years after ACLR during triple hops (TH), single hop (TH), single-legged vertical jump (VJ), and walking.

METHODS

Forty-one athletes with 2 years of unilateral ACLR surgery participated in this cross-sectional study. Athletes completed motion analysis testing of single-legged TH, SH, VJ, and walking tasks. Sagittal plane TSM and individual joint (ankle, knee, and hip) contributions to TSM were computed at peak knee flexion angle (TSM-PKF). Posterior-anterior radiographs were completed in standing and 30° knee flexion. Kellgren-Lawrence (KL) system was used to identify radiological features of knee OA in the medial compartment of the reconstructed knee (OA-group: KL ≥2; Non-OA group: KL<2).

RESULTS

There was a significant group-by-joint-by-task interaction for joint contributions to TSM-PKF (p = 0.012), with the OA-group (n = 13) had lower knee and higher hip contributions compared to the non-OA group during TH, SH, and VJ (p ≤ 0.049). There was a significant joint-by-group interaction for the joint contributions to TSM-PKF (p = 0.004), with the OA-group having lower knee (p = 0.003) and higher hip (p = 0.001) contributions compared to the Non-OA group.

SIGNIFICANCE

The OA-group exhibited lower knee and higher hip contributions to the sagittal plane TSM compared to the Non-OA group during the landing phase of single-limb high-demand activities. The OA-group exhibited decreased knee loading and compensated by shifting the mechanical load to the hip joint within the reconstructed knee. Decreased knee loading in the OA-group may have affected the required mechanical loading to maintain knee metabolism and integrity.

Cartilage deformation following a walking bout in individuals with anterior cruciate ligament reconstruction

The purpose was to (1) compare the effect of a walking bout on femoral cartilage deformation between limbs with and without anterior cruciate ligament reconstruction (ACLR) and (2) examine the association between gait kinetics and the magnitude of cartilage deformation. A total of 30 individuals with primary unilateral ACLR completed this study [14 male, 16 female; age = 22.57 (3.78) years; body mass index (BMI) = 25.88 (5.68) kg/m2 ; time since ACLR = 61.00 (16.43) months]. Overground walking biomechanics were assessed on day 1, and a 30-min walking bout or 30-min resting bout (control) were completed on days 2 and 3 (counterbalanced order). Femoral cartilage thickness was measured using ultrasound before, immediately following, and 30-min following each intervention. Linear mixed effects models compared the effect of walking on cartilage thickness between the ACLR and contralateral limbs after adjusting for sex, BMI, speed, and the number of steps. Stepwise regression examined the association between the external knee flexion and adduction moments and cartilage deformation following walking. There was a significant limb × time interaction for medial cartilage thickness. Post hoc analyses indicated that cartilage thickness decreased immediately following walking in the contralateral but not ACLR limb. Main effects of limb were observed for medial, central, and lateral cartilage thickness indicating thicker cartilage in the ACLR compared with contralateral limb. A higher knee adduction moment was associated with greater cartilage deformation in the ACLR limb. Femoral cartilage in the ACLR limb exhibited a less dynamic response to walking than the uninvolved limb, which may be due to habitual underloading during gait.

Incidence of and Risk Factors for Arthrogenic Muscle Inhibition in Acute Anterior Cruciate Ligament Injuries: A Cross-Sectional Study and Analysis of Associated Factors From the SANTI Study Group

BACKGROUND

Arthrogenic muscle inhibition (AMI) is a process in which neural inhibition after injury or surgery to the knee results in quadriceps activation failure and knee extension deficit.

PURPOSE

To determine the incidence and spectrum of the severity of AMI after acute anterior cruciate ligament (ACL) injury using the Sonnery-Cottet classification, to determine the interobserver reliability of the classification system, and to investigate potential important factors associated with AMI after ACL injury.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

Consecutive patients who had an acute ACL injury between October 2021 and February 2022 were considered for study inclusion. Eligible patients underwent a standardized physical examination at their first outpatient appointment. This included an assessment of quadriceps inhibition, identification of any extension deficits, and grading of AMI and its reversibility according to the Sonnery-Cottet classification.

RESULTS

A total of 300 consecutive patients with acute ACL ruptures were prospectively enrolled in the study. Of them, 170 patients (56.7%) had AMI. Patients evaluated with AMI showed a significantly inferior Lysholm score, International Knee Documentation Committee score, Simple Knee Value, and Knee injury and Osteoarthritis Outcome Score than patients without AMI (P < .0001). Multivariate analysis revealed that the presence of effusion, concomitant injuries, and high pain scores were associated with a significantly greater risk of AMI. Additional associations with the presence of AMI included a short duration between injury and evaluation, the use of crutches, and using a pillow as a support at night. In contrast, a previous ACL injury was associated with significantly lower odds of developing AMI (OR, 0.025; 95% CI, 0-0.2; P = .014). Among the 170 patients with AMI, 135 patients (79%) showed a resolution of their inhibition at the end of the consultation after application of simple exercises; the remaining 35 patients required specific rehabilitation. Interobserver reliability of the classification system was almost perfect (95% CI, 0.86-0.99).

CONCLUSION

AMI occurs in over half of patients with acute ACL injuries. When it occurs, it is easily reversible in the majority of patients with simple exercises targeted at abolishing AMI. The presence of "red flags" should increase the index of suspicion for the presence of AMI, and these include the presence of an effusion, high pain scores, a short time between injury and evaluation, multiligament injuries, the use of crutches, and using a pillow as a support at night. Patients with a history of ipsilateral or contralateral ACL injury are at a significantly lower risk of AMI than those with a first-time ACL injury.

Optimising the Early-Stage Rehabilitation Process Post-ACL Reconstruction

Outcomes following anterior cruciate ligament reconstruction (ACLR) need improving, with poor return-to-sport rates and a high risk of secondary re-injury. There is a need to improve rehabilitation strategies post-ACLR, if we can support enhanced patient outcomes. This paper discusses how to optimise the early-stage rehabilitation process post-ACLR. Early-stage rehabilitation is the vital foundation on which successful rehabilitation post-ACLR can occur. Without high-quality early-stage (and pre-operative) rehabilitation, patients often do not overcome major aspects of dysfunction, which limits knee function and the ability to transition through subsequent stages of rehabilitation optimally. We highlight six main dimensions during the early stage: (1) pain and swelling; (2) knee joint range of motion; (3) arthrogenic muscle inhibition and muscle strength; (4) movement quality/neuromuscular control during activities of daily living (5) psycho-social-cultural and environmental factors and (6) physical fitness preservation. The six do not share equal importance and the extent of time commitment devoted to each will depend on the individual patient. The paper provides recommendations on how to implement these into practice, discussing training planning and programming, and suggests specific screening to monitor work and when the athlete can progress to the next stage (e.g. mid-stage rehabilitation entry criteria).

Which Tests Predict 6-Month Isokinetic Quadriceps Strength After ACL Reconstruction? An Examination of Isometric Quadriceps Strength and Functional Tests at 3 Months

Background

Restoration of quadriceps strength after anterior ligament reconstruction (ACLR) is a persistent challenge for patients and clinicians. Inadequate recovery of quadriceps strength has been linked to increase risk of re-injury. Developing methods of early identification of strength deficits is essential to allow clinicians to provide more individualized interventions early in the rehabilitation process.

Purpose

To determine whether 3-month isometric quadriceps strength, the Y-Balance Test (YBT), and the anterior step-down test are predictive of isokinetic quadriceps strength at six months in adolescents after ACLR.

Design

Retrospective cohort.

Methods

Thirty-six adolescent patients with primary ACLR (58% female, 36% with concomitant meniscal repair, age: 15.7 ± 1.6 years). At three months post-operative, isometric quadriceps strength via isokinetic dynamometer, YBT-Lower Quarter, and anterior step-down tests were completed. At six months post-operative, an isokinetic knee strength assessment was completed. Regression analysis was used to evaluate the predictive relationship between 3-month isometric tests and 6-month isokinetic knee extension tests.

Results

Three-month post operative isometric quadriceps peak torque predicted isokinetic quadriceps peak torque at 6 months, F(1,34) = 19.61, p <0.001. Three-month isometric quadriceps peak torque accounted for 36.6% of the variance in normalized isokinetic quadriceps peak torque at 6 months with adjusted R2 = 34.7%. Including YBT anterior reach (β = 0.157, p = 0.318) in regression added 1.9% of variance when predicting 6-month isokinetic quadriceps peak torque, F (2,33) = 10.32, p <0.001, R2 = 0.385, ΔR2 = 0.019.

Conclusion

At three months post-ACLR, isometric strength testing appears more optimal than other functional tests in predicting isokinetic quadriceps peak torque in later stages of rehabilitation for adolescents. Clinicians should use tests at three months that measure quadriceps strength if aiming to predict isokinetic quadriceps peak torque at six months post-ACLR, rather than using functional tests such as the YBT-LQ or anterior step-down.

Level of Evidence

Level 3.

Risk Factors for Ipsilateral Versus Contralateral Reinjury After ACL Reconstruction in Athletes: A Systematic Review and Meta-analysis

Background

Anterior cruciate ligament (ACL) reinjury after ACL reconstruction (ACLR) can occur on the ipsilateral or contralateral side. Limited evidence exists regarding the difference between the incidence of reinjury to either knee, which is important in developing interventions to prevent ACL reinjury.

Purpose

To compare the reinjury rate of the ACL on the ipsilateral side versus the contralateral side in athletes after ACLR and investigate the risk factors that may cause different reinjury rates between the sides.

Study Design

Systematic review; Level of evidence, 4.

Methods

A systematic review was performed based on the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Studies that involved ACL reinjury in athletes after ACLR were reviewed. Considering several risk factors, including age and sex, a comparison of ACL reinjury incidence on the ipsilateral and contralateral sides was performed using a meta-analysis.

Results

Of the 17 selected studies, 3 were found to be at high risk of bias, and thus, 14 (n = 3424 participants) studies were included in the meta-analysis. In this athletic population, the contralateral ACL had a significantly higher rupture rate than the ipsilateral graft (risk ratio [RR], 1.41; P < .0001). Female athletes were found to have a greater risk of ACL reinjury on the contralateral versus the ipsilateral side (RR, 1.65; P = .0005), but different results were found in male athletes. (RR, 0.81; P = .21). There was no statistical difference in the incidence rate of ACL reinjury to either side in adolescent athletes (RR, 1.15; P = .28).

Conclusion

The contralateral ACL was more vulnerable to reinjury than the ipsilateral side in athletes after ACLR. Female athletes were more likely to reinjure their contralateral native ACL, while the same trend was not found in their male counterparts. The reinjury rate was comparable in both knees in adolescent athletes.

Pain Early After Anterior Cruciate Ligament Reconstruction is Associated With 6-Month Loading Mechanics During Running

BACKGROUND

Anterior cruciate ligament reconstruction (ACLR) results in persistent altered knee biomechanics, but contributing factors such as pain or patient function, leading to the altered loading, are unknown.

HYPOTHESIS

Individuals with worse self-reported pain after ACLR would have poorer biomechanics during running, and poor loading mechanics would be present in the ACLR limb compared with contralateral and control limbs.

STUDY DESIGN

Cohort pilot study.

LEVEL OF EVIDENCE

Level 3.

METHODS

A total of 20 patients after ACLR (age, 18.4 ± 2.7 years; height, 1.7 ± 0.1 m; mass, 84.2 ± 19.4 kg) completed visual analog scale and Knee Injury and Osteoarthritis Outcomes Score (KOOS) at 1 and 6 months postsurgery. At 6 months postsurgery, patients underwent biomechanical testing during running. A total of 20 control individuals also completed running biomechanical analyses. Associations between patient outcomes and biomechanics were conducted, and differences in running biomechanics between groups were analyzed.

RESULTS

KOOS pain score 1 month after surgery was associated with peak ACLR knee abduction moment (R2 = 0.35;P = 0.01). At 6-months, KOOS sport score was related to peak abduction moment in the ACLR limb (R2 = 0.23; P = 0.05). For change scores, the improvement in pain scores related to ACLR limb peak knee abduction moment (R2 = 0.55; P = 0.001). The ACLR limb had lower knee excursion, extension moments, and ground-reaction forces compared with the uninvolved and control limb. The uninvolved limb also had higher ground-reaction forces compared with the ACLR limb and control limb.

CONCLUSION

These results suggest that patient-reported outcomes 1 and 6 months after surgery are associated with running mechanics 6 months after ACLR. Further, the underloading present in the ACLR limb and overloading in the uninvolved limb indicates greater need for running rehabilitation after ACLR.

CLINICAL RELEVANCE

Understanding pain and how it may be linked to movement dysfunction is important for improving long-term outcomes.

Factors Associated With Sports Function and Psychological Readiness to Return to Sports at 12 Months After Anterior Cruciate Ligament Reconstruction: A Cross-sectional Study

BACKGROUND

Sports function and psychological readiness to return to sports (RTS) are important outcomes when evaluating rehabilitation after anterior cruciate ligament reconstruction (ACLR). It is, however, unclear which specific factors contribute most to these outcomes.

PURPOSE

To determine associations between demographic characteristics, objective measurements of physical function, patient-reported outcome measure scores, sports-related function assessed with the Knee injury and Osteoarthritis Outcome Score (KOOS) Sport and Recreation subscale, and psychological readiness to RTS assessed with the Anterior Cruciate Ligament-Return to Sport after Injury (ACL-RSI) scale at 1 year after ACLR.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

At a mean of 12.5 ± 2.0 months after ACLR, 143 participants (50.3% female), with a mean age of 25.0 ± 5.7 years, were assessed for demographic characteristics, physical factors (hop performance, muscle strength, ankle and hip range of motion), and psychological factors (KOOS Pain and Symptoms subscales, Perceived Stress Scale, fear of reinjury) as well as the KOOS Sport and Recreation subscale and ACL-RSI scale. Backward linear regression models were used to evaluate factors associated with sports function and psychological readiness to RTS.

RESULTS

Lower isokinetic knee extension peak torque (limb symmetry index) (B = 18.38 [95% CI, 3.01-33.75]), lower preinjury activity level (B = 2.00 [95% CI, 0.87-3.14]), greater knee pain (B = 0.90 [95% CI, 0.70-1.10]), shorter time between injury and reconstruction (B = 0.16 [95% CI, 0.05-0.26]), and greater fear of reinjury (B = 0.11 [95% CI, 0.01-0.20]) were associated with a worse KOOS Sport and Recreation subscore (R2 = 0.683). A shorter hop distance (B = 0.15 [95% CI, 0.00-0.29]) was associated with a lower ACL-RSI score (R2 = 0.245).

CONCLUSION

A combination of knee muscle strength, activity level, knee pain, timing of surgery, and fear of reinjury accounted for approximately 70% of the variation in sports function at 1 year after ACLR. In contrast, there was only 1 weak association between physical function and psychological readiness to RTS at this time point. Thus, factors associated with current sports function are much better known than features related to psychological readiness to RTS.

The Influence of Quadriceps Strength and Rate of Torque Development on the Recovery of Knee Biomechanics During Running After Anterior Cruciate Ligament Reconstruction

BACKGROUND

After anterior cruciate ligament reconstruction (ACLR), altered surgical knee biomechanics during running is common. Although greater quadriceps strength is associated with more symmetrical running knee kinetics after ACLR, abnormal running mechanics persist even after resolution of quadriceps strength deficits. As running is a submaximal effort task characterized by limited time to develop knee extensor torque, quadriceps rate of torque development (RTD) may be more closely associated with recovery of running knee mechanics than peak torque (PT).

PURPOSE

To assess the influence of recovery in quadriceps PT and RTD symmetry on knee kinematic and kinetic symmetry during running over the initial 2 years after ACLR.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A total of 39 Division I collegiate athletes (106 testing sessions; 19 female) completed serial isometric performance testing and running analyses between 3 and 24 months after ACLR. Athletes performed maximal and rapid isometric knee extension efforts with each limb to assess PT and RTD between-limb symmetry indices (PTLSI and RTDLSI), respectively. Peak knee flexion difference (PKFDIFF) and peak knee extensor moment limb symmetry index (PKEMLSI) during running were computed. Multivariable linear mixed-effects models assessed the influence of PTLSI and RTDLSI on PKFDIFF and PKEMLSI over the initial 2 years after ACLR.

RESULTS

Significant main effects of RTDLSI (P < .001) and time (P≤ .02) but not PTLSI (P≥ .24) were observed for both PKFDIFF and PKEMLSI models. For a 10% increase in RTDLSI, while controlling for PTLSI and time, a 0.9° (95% CI, 0.5°-1.3°) reduction in PKFDIFF and a 3.5% (95% CI, 1.9%-5.1%) increase in PKEMLSI are expected. For every month after ACLR, a 0.2° (95% CI, 0.1°-0.4°) reduction in PKFDIFF and a 1.3% (95% CI, 0.6%-2.0%) increase in PKEMLSI are expected, controlling for PTLSI and RTDLSI.

CONCLUSION

Quadriceps RTDLSI was more strongly associated with symmetrical knee biomechanics during running compared with PTLSI or time throughout the first 2 years after ACLR.

Is quadriceps strength associated with patellofemoral joint loading after anterior cruciate ligament reconstruction?

OBJECTIVE

To test whether quadriceps strength is associated with measures of patellofemoral (PF) joint loading during running and hopping in people after an anterior cruciate ligament reconstruction (ACLR).

DESIGN

Cross-sectional study.

SETTING

Biomechanics laboratory.

PARTICIPANTS

Sixty-five participants (24 women; 41 men) 1-2 years post-ACLR.

MAIN OUTCOME MEASURES

Peak isometric quadriceps strength for the surgical limb was measured using a dynamometer. Motion analysis and ground reaction force data were combined with musculoskeletal modelling to measure PF joint loading variables for the reconstructed knee (peak knee flexion angle; peak/impulse of the PF joint contact force; time to peak PF joint contact force) during the stance phase of running and during the landing phase of a standardised forward hop. Linear regression analysis (adjusting for age and sex) assessed the association between quadriceps strength and PF joint loading variables.

RESULTS

Two significant, albeit modest, associations were revealed. Quadriceps strength was associated with the time to peak PF joint contact force during running (β = -0.001; 95%CI -0.002 to -0.000; R2 = 0.179) and the impulse of the PF joint contact force during hopping (β = 0.014; 95%CI 0.003 to 0.024; R2 = 0.159).

CONCLUSIONS

A strong link between quadriceps strength and PF joint loading was not evident in people 1-2 years post-ACLR.

Quadriceps Performance and Running Biomechanics Influence Femur BMD Changes after ACL Reconstruction in Collegiate Athletes

PURPOSE

Reduced bone mineral density of the distal femur (BMD DF ) can persist long term after anterior cruciate ligament reconstruction (ACLR), even in athletes who return to high levels of competition. These deficits may have implications for the onset and progression of knee osteoarthritis. It is unknown if clinically modifiable factors are associated with losses in BMD DF . This study evaluated the potential influence of knee extensor peak torque (PT), rate of torque development (RTD), as well as peak knee flexion (PKF) angle and peak knee extensor moment (PKEM) during running, on longitudinal changes in BMD DF post-ACLR.

METHODS

After ACLR, 57 Division I collegiate athletes underwent serial whole-body dual-energy x-ray absorptiometry (DXA) scans between 3 and 24 months post-ACLR. Of these, 43 athletes also had isometric knee extensor testing (21 female, 105 observations), and 54 had running analyses (26 female, 141 observations). Linear mixed-effects models, controlling for sex, assessed the influence of surgical limb quadriceps performance (PT and RTD), running mechanics (PKF and PKEM), and time post-ACLR on BMD DF (5% and 15% of femur length). Simple slope analyses were used to explore interactions.

RESULTS

Athletes with RTD less than 7.20 (N·m)·kg -1 ·s -1 (mean) at 9.3 months post-ACLR demonstrated significant decreases in 15% BMD DF over time ( P = 0.03). Athletes with PKEM during running less than 0.92 (N·m)·kg -1 (-1 SD below mean) at 9.8 months post-ACLR demonstrated significant decreases in 15% BMD DF over time ( P = 0.02). Significant slopes were not detected at -1 SD below the mean for PT (1.75 (N·m)·kg -1 , P = 0.07) and PKF (31.3°, P = 0.08).

CONCLUSIONS

Worse quadriceps RTD and running PKEM were associated with a greater loss of BMD DF between 3 and 24 months post-ACLR.

Muscle function, Lysholm score and hop performance in individuals with clinical indications for the combined reconstruction of the anterior cruciate and the anterolateral ligaments of the knee: A cross-sectional study

OBJECTIVE

To evaluate hip and knee muscular function, knee patient-reported outcome measures and hop performance in patients with a clinical indication for combined ACL+ALL reconstruction surgery compared to patients with an isolated ACL reconstruction surgery indication (preoperative phase) and to a control group.

DESIGN

Cross-sectional study.

METHODS

The sample was composed of male individuals, aged between 18 and 59 years, divided into three groups (ACL, ACL+ALL and Control). Isokinetic dynamometry was performed for the flexor and extensor knee muscles and for the hip abductors and adductors. SLHT, COHT and the Lysholm score were performed. Pain, swelling, and thigh trophism were also measured.

RESULTS

The study participants were 89 male individuals: 63 in the injury group and 26 in the control group. After applying the criteria for an ALL reconstruction indication, 33 patients were assigned to the ACL Group and 30 patients to the ACL+ALL Group. Regarding knee and hip muscle function, both groups presented worse results when compared to the control group, however, did not show significant differences compared to each other. Regarding the functional variables, the ACL+ALL group showed a significantly shorter distance achieved in the Crossover Hop Test than the other groups, as well as more pain during the tests.

CONCLUSION

Knee and hip muscular functions are impaired after an ACL injury and do not seem to be influenced or worsened in individuals with greater rotational instability with clinical indications for combined reconstruction of the anterior cruciate and the anterolateral ligaments of the knee.

Investigating the effect of sand training on running mechanics in individuals with anterior cruciate ligament reconstruction and pronated feet

BACKGROUND

Running on sand could be a method for the rehabilitation of individuals with anterior cruciate ligament reconstruction and pronated feet. However, there is a lack of knowledge about the effects of running on sand on running biomechanics and muscle activities.

RESEARCH QUESTION

What is the effect of sand training on running mechanics in individuals with anterior cruciate ligament reconstruction and pronated feet?

METHODS

Twenty-eight adult males with anterior cruciate ligament reconstruction and pronated feet were divided into two equal groups (intervention and active control groups). Participants were asked to run at a constant speed of ∼3.2 m/s over an 18 m runway, respectively. Ground reaction forces were recorded using a Bertec force plate. Muscle activities were recorded using a surface bipolar electromyography system.

RESULTS

In intervention group but not control group, post-hoc analysis demonstrated significantly longer time-to-peak of impact vertical ground reaction force at post-test than that pre-test (p = 0.047). In intervention group but not control group, post-hoc analysis demonstrated significant decreases of semitendinosus activities during push-off at post-test compared with the pre-test (p = 0.005).

SIGNIFICANCE

Sand training improved time-to-peak of ground reaction forces (e.g., time-to-peak of peak of impact vertical ground reaction force) and muscle activities (e.g., semitendinosus activities) in adult males with anterior cruciate ligament reconstruction and pronated feet.

Brain activity associated with quadriceps strength deficits after anterior cruciate ligament reconstruction

Prolonged treatment resistant quadriceps weakness after anterior cruciate ligament reconstruction (ACL-R) contributes to re-injury risk, poor patient outcomes, and earlier development of osteoarthritis. The origin of post-injury weakness is in part neurological in nature, but it is unknown whether regional brain activity is related to clinical metrics of quadriceps weakness. Thus, the purpose of this investigation was to better understand the neural contributions to quadriceps weakness after injury by evaluating the relationship between brain activity for a quadriceps-dominated knee task (repeated cycles of unilateral knee flexion/extension from 45° to 0°), , and strength asymmetry in individuals returned to activity after ACL-R. Forty-four participants were recruited (22 with unilateral ACL reconstruction; 22 controls) and peak isokinetic knee extensor torque was assessed at 60°/s to calculate quadriceps limb symmetry index (Q-LSI, ratio of involved/uninvolved limb). Correlations were used to determine the relationship of mean % signal change within key sensorimotor brain regions and Q-LSI. Brain activity was also evaluated group wise based on clinical recommendations for strength (Q-LSI < 90%, n = 12; Q-LSI ≥ 90%, n = 10; controls, all n = 22 Q-LSI ≥ 90%). Lower Q-LSI was related to increased activity in the contralateral premotor cortex and lingual gyrus (p < .05). Those who did not meet clinical recommendations for strength demonstrated greater lingual gyrus activity compared to those who met clinical recommendations Q-LSI ≥ 90 and healthy controls (p < 0.05). Asymmetrically weak ACL-R patients displayed greater cortical activity than patients with no underlying asymmetry and healthy controls.

Beyond peak torque: Longitudinal analysis of angle-specific isokinetic knee torques in collegiate athletes post-ACLR

OBJECTIVES

To investigate changes in angle-specific knee extensor torque between limbs from 4 to 12 months post-anterior cruciate ligament reconstruction(ACLR) in Division I collegiate athletes at two different isokinetic velocities.

DESIGN

Case-series study.

SETTING

Laboratory-based.

PARTICIPANTS

Isokinetic knee flexion and extension assessments of 17 athletes (11 female) at 4, 8, and 12 months after ACLR with bone-patellar tendon-bone autograft were evaluated.

MAIN OUTCOME MEASURES

Angle-specific curve analyses were performed using statistical parametric mapping for torque data obtained between 14 and 101° at 60°/s and 240°/s velocities.

RESULTS

At 60°/s, knee extensor torque of the operated limb increased between 4 and 8 months (18-101°,p < 0.001), 4 and 12 months (28-101°,p < 0.001), and 8 and 12 months post-surgery (62-70°,p = 0.002, and 79-90°,p < 0.001). Knee extensor torque was lower in the operated limb compared to the non-operated limb at 4 (47-97°,p < 0.001) and 8 months (65-90°,p < 0.001) for 60°/s, at 4 (21-89°,p < 0.001) and 8 months (50-77°,p < 0.001) for 240°/s, with no between-limb differences at 12 months post-ACLR for both velocities.

CONCLUSIONS

Operated limb knee extensor torque increased throughout the majority of knee range of motion from 4 to 12 months post-ACLR at both isokinetic velocities, while non-operated limb torque only improved through a reduced arc of motion in greater knee flexion angles.

Knee kinetics and the medial femoral cartilage cross-sectional area response to loading in indviduals with anterior cruciate ligament reconstruction

BACKGROUND

Ultrasonography is capable of detecting morphological changes in femoral articular cartilage cross-sectional area in response to an acute bout of walking; yet, the response of femoral cartilage cross-sectional area varies between individuals. It is hypothesized that differences in joint kinetics may influence the response of cartilage to a standardized walking protocol. Therefore, the study purpose was to compare internal knee abduction and extension moments between individuals with anterior cruciate ligament reconstruction who demonstrate an acute increase, decrease, or unchanged medial femoral cross-sectional area response following 3000 steps.

METHODS

The medial femoral cartilage in the anterior cruciate ligament reconstructed limb was assessed with ultrasonography before and immediately following 3000 steps of treadmill walking. Knee joint moments were calculated in the anterior cruciate ligament reconstructed limb and compared between groups throughout the stance phase of gait using linear regression and functional, mixed effects waveform analyses.

FINDINGS

No associations between peak knee joint moments and the cross-sectional area response were observed. The group that demonstrated an acute cross-sectional area increase exhibited 1) lower knee abduction moments in early stance in comparison to the group that exhibited a decreased cross-sectional area response; and 2) greater knee extension moments in early stance in comparison to the group with an unchanged cross-sectional area response.

INTERPRETATION

The propensity of femoral cartilage to acutely increase cross-sectional area in response to walking is consistent with less-dynamic knee abduction and knee extension moment profiles.

The effects of different rehabilitation training modalities on isokinetic muscle function and male athletes' psychological status after anterior cruciate ligament reconstructions

BACKGROUND

Previously, researchers reported performance enhancements following long-term plyometric training in athletes with anterior cruciate ligament reconstruction (LCA). However, the effects of combined eccentric and plyometric training on measures of isokinetic strength and psychological statues in male athletes have not been examined yet. Knowledge on the effects of combined eccentric and plyometric training help to better plan and program rehabilitations sessions and thus return-to-sports.

OBJECTIVE

This study sought to compare the effects of three different rehabilitation training programs, eccentric training (ECC), plyometric training (PLYO), or combined eccentric and plyometric training (COMB), on psychological measures (kinesiophobia [TSK-CF], functional knee assessment, knee injury and osteoarthritis outcome score [KOOS], international knee documentation committee 2000 questionnaire [IKDC], and knee flexor and extensor isokinetic muscle performance (peak torque [PT], total work, ratio [R-HQ], and ratio of total work [R-TW]) at different angular velocities post ACL surgery in male elite athletes.

METHODS

Forty elite male athletes from different sports (e.g., athletics, team sports) with ACL reconstruction participated in this study. The study started after a 14-weeks post-surgery rehabilitation program, which was identical for all subjects. After this initial rehabilitation period, athletes were randomly assigned to three experimental groups, ECC (n = 10), PLYO (n = 10), and COMB (n = 10), and a control group (CON: n = 10). Testing was conducted pre- and post-the 6-weeks intervention period and included the TSK-CF, KOOS, and IKDC. Peak torque of the knee extensors/flexors was tested at 90, 180, 240 °/s, after the 6-weeks training program only.

RESULTS

Participants' adherence rate was 100% across all groups and none reported any training or test-related injury. No significant between-group baseline differences (pre-6-weeks intervention) were observed for any of the reported psychological and muscle strength parameters. Significant group-by-time interactions were found for TSK-CF (p = 0.001, d = 2.85), KOOS (p = 0.001, d = 1.31), and IKDC (p = 0.001, d = 1.07). The post-hoc analyses indicated that COMB showed larger pre-post improvements for all psychological variables (p < 0.001, d = 2.95 to 13.15), compared with PLYO, ECC, and CON. Contrast analyses demonstrated that COMB yielded significantly greater improvements compared with CON, PLYO, ECC for all isokinetic parameters at all three angular velocities (all p < 0.001, d = 0.99 to 4.61).

CONCLUSION

The results showed that COMB induced greater gains for measures of psychological status and isokinetic muscle strength compared with single-mode PLYO and ECC in elite male athletes during a post-surgery ACL rehabilitation period. Accordingly, it is recommended to implement COMB as an effective rehabilitation means to improve knee function in male elite athletes.

TRIAL REGISTRATION

This study does not report results related to health care interventions using human participants and therefore it was not prospectively registered.

Surface electromyography characteristics of patients with anterior cruciate ligament injury in different rehabilitation phases

Background: Anterior cruciate ligament reconstruction (ACLR) is a common treatment for anterior cruciate ligament (ACL) injury. However, after ACLR, a significant proportion of patients do not return to pre-injury levels. Research on muscle function during movement has important implications in rehabilitation.

Methods: Sixty patients with unilateral ACL injury were recruited for this study and assigned into three groups: group A, individuals with an ACL injury before 6 months; group B, individuals with ACLR from 6 months to 1 year; and group C, individuals with ACLR 1 year later. Surface electromyography (SEMG) signals were collected from the bilateral rectus femoris (RF), vastus medialis (VM), vastus lateralis (VL), biceps femoris (BF), and semitendinosus (ST). The tasks performed during the experiment included straight leg raising (SLR) training at 30°, SLR training at 60°, ankle dorsiflexion, walking, and fast walking.

Results: In the maximum muscle strength test, the affected side of the BF in group A (199.4 ± 177.12) was significantly larger than in group B (53.91 ± 36.61, p = 0.02) and group C (75.08 ± 59.7, p = 0.023). In the walking test, the contralateral side of the RF in group B (347.53 ± 518.88) was significantly greater than that in group C (139.28 ± 173.78, p = 0.029). In the SLR training (60°) test, the contralateral side of the RF in group C (165.37 ± 183.06) was significantly larger than that in group A (115.09 ± 62.47, p = 0.023) and smaller than that in group B (226.21 ± 237.17, p = 0.046); In the ankle dorsiflexion training test, the contralateral side of the RF in group B (80.37 ± 87.9) was significantly larger than that in group C (45.61 ± 37.93, p = 0.046).

Conclusion: This study showed the EMG characteristics of patients with ACL injury helped to determine which muscle requires more training and which exercise model would be best suited for intervention.

Medial congruent polyethylene design show different tibiofemoral kinematics and enhanced congruency compared to a standard symmetrical cruciate retaining design for total knee arthroplasty-an in vivo randomized controlled study of gait using dynamic radiostereometry

PURPOSE

New total knee arthroplasty implant designs attempt to normalize kinematics patterns that may improve functional performance and patient satisfaction. It was hypothesized that a more medial congruent (MC) anatomic bearing design (1) influences the tibiofemoral kinematics and (2) enhances articular congruency compared to a standard symmetrical cruciate retaining (CR) bearing design.

METHODS

In this double-blinded randomized study, 66 patients with knee osteoarthritis were randomly included in two groups: MC (n = 31) and CR (n = 33). Clinical characteristics such as knee ligament lesions and knee osteoarthritis scores were graded on preoperative magnetic resonance imaging and radiography. At the 1-year follow-up, dynamic radiostereometric analysis was used to assess tibiofemoral joint kinematics and articulation congruency. Patient-reported outcome measures, Oxford Knee Score, the Forgotten Joint Score, and the Knee Osteoarthritis Outcome Score, were assessed preoperatively and at the 1-year follow-up.

RESULTS

Compared to the CR bearing, the MC bearing displayed an offset with approximately 3 mm greater anterior tibial drawer (p < 0.001) during the entire motion, and up to approximately 3.5 degrees more tibial external rotation (p = 0.004) from mid-swing to the end of the gait cycle at the 1-year follow-up. Furthermore, the congruency area in the joint articulation was larger during approximately 80% of the gait cycle for the MC bearing compared to the CR. The patient-reported outcome measures improved (p < 0.001), but there were no differences between groups. In addition, there were no differences in clinical characteristics and there were no knee revisions or recognized deep infections during follow-up.

CONCLUSION

The study demonstrates that the MC-bearing design changes tibiofemoral kinematics and increases the area of congruency towards more native knee kinematics than the CR bearing. In perspective this may contribute to a more stabilized knee motion, restoring the patient's confidence in knee function during daily activities.

Native knee kinematics is not reproduced after sensor guided cruciates substituting total knee arthroplasty

PURPOSE

Gait analysis was used to evaluate knee kinematics in patients who underwent successful primary total knee arthroplasty (TKA) using two modern bi-cruciate substituting designs. The knee joint was balanced intraoperatively using real-time sensor technology, developed to provide dynamic feedback regarding stability and tibiofemoral load. The authors hypothesized that major differences exist in gait parameters between healthy controls and post-TKA patients.

METHODS

Ten patients who underwent successful TKA using bi-cruciate substituting designs were evaluated at a minimum of 9 months postoperatively using three-dimensional knee kinematic analysis; a multi-camera optoelectronic system and a force platform were used. Sensor-extracted kinematic data included knee flexion angle at heel-strike (KFH), peak midstance knee flexion angle (MSKFA), maximum and minimum knee adduction angle (KAA) and knee rotational angle at heel-strike. Multiple gait analysis data from the study group were compared to a group of ten healthy controls who were matched by age, sex and BMI. Clinical outcome in the TKA group was also measured using the Knee injury and Osteoarthritis Outcome Score (KOOS).

RESULTS

Clinically, at final follow-up, a statistically significant difference in pain, general symptoms, and activities of daily living was seen between the groups. From a gait analysis standpoint, TKA patients had significantly less rotation at heel strike (p = 0.04), lower late stance peak extension moments (p = 0.02), and less Knee Adduction Angle excursion during swing phase (p = 0.04) compared to the control group. No statistically significant difference was observed for knee flexion angle at heel strike, knee adduction moment, or peak knee flexion moment between the groups.

CONCLUSIONS

Modern bi-cruciate substituting TKA designs failed to reproduce normal knee kinematics. The lack of full knee extension during the stance phase, absence of the "screw-home mechanism" typical of an ACL functioning knee, and the reduced fluctuation in knee adduction angle during the swing phase still represent major proprioceptive and muscular recruitment differences between normal and replaced knees.

Comparison of discrete and continuous analysis approaches for evaluating gait biomechanics in individuals with anterior cruciate ligament reconstruction

BACKGROUND

Aberrant gait biomechanics contribute to post-traumatic knee osteoarthritis development following anterior cruciate ligament reconstruction (ACLR). Walking gait biomechanics are typically evaluated post-ACLR by identifying discrete, peak values in the load acceptance phase of gait (i.e. first 50 %). As these approaches evaluate a single time instant during the gait cycle, functional data analysis (FDA) techniques that evaluate the entire stance phase waveform are becoming more common in the literature. However, it is unclear if these analysis approaches identify the same biomechanical phenomena.

RESEARCH QUESTION

The purpose of this study was to determine whether four gait biomechanics analysis approaches identify the same aberrant gait characteristics in individuals with ACLR.

METHODS

Twenty-four individuals with ACLR and 24 healthy controls completed gait analyses on an instrumented treadmill. Four analysis approaches were employed to compare the vertical ground reaction force and sagittal knee angles and moments during the first 50 % of the stance phase between groups and between limbs in the ACLR cohort: 1) comparison of peak values from individual trials (Peak), 2) comparison of peak values from time-normalized ensemble waveforms (Ensemble Peak), 3) FDA via functional ANCOVA (FANCOVA), and 4) FDA evaluating overlap of the 95 % confidence intervals for each waveform (FDA-CI).

RESULTS

The Peak, Ensemble Peak, and FANCOVA approaches identified highly similar group and limb differences in the biomechanics outcomes with respect to both magnitude and temporal location. However, the FANCOVA approach indicated that these differences were distributed across large portions of the load acceptance phase and that differences existed outside the first 50 % of stance. The FDA-CI approach was generally not effective for identifying aberrant gait biomechanics.

SIGNIFICANCE

Peak and FANCOVA approaches to gait analysis provide similar findings. Future research is necessary to determine if the additional information afforded by FANCOVA provides insight regarding the mechanical pathogenesis of post-traumatic knee osteoarthritis.

Evaluating the risk of knee osteoarthritis following unilateral ACL reconstruction based on an EMG-assisted method

Objective: Anterior cruciate ligament reconstruction (ACLR) cannot decrease the risk of knee osteoarthritis after anterior cruciate ligament rupture, and tibial contact force is associated with the development of knee osteoarthritis. The purpose of this study was to compare the difference in bilateral tibial contact force for patients with unilateral ACLR during walking and jogging based on an EMG-assisted method in order to evaluate the risk of knee osteoarthritis following unilateral ACLR. Methods: Seven unilateral ACLR patients participated in experiments. The 14-camera motion capture system, 3-Dimension force plate, and wireless EMG test system were used to collect the participants' kinematics, kinetics, and EMG data during walking and jogging. A personalized neuromusculoskeletal model was established by combining scaling and calibration optimization. The inverse kinematics and inverse dynamics algorithms were used to calculate the joint angle and joint net moment. The EMG-assisted model was used to calculate the muscle force. On this basis, the contact force of the knee joint was analyzed, and the tibial contact force was obtained. The paired sample t-test was used to analyze the difference between the participants' healthy and surgical sides of the participants. Results: During jogging, the peak tibial compression force on the healthy side was higher than on the surgical side (p = 0.039). At the peak moment of tibial compression force, the muscle force of the rectus femoris (p = 0.035) and vastus medialis (p = 0.036) on the healthy side was significantly higher than that on the surgical side; the knee flexion (p = 0.042) and ankle dorsiflexion (p = 0.046) angle on the healthy side was higher than that on the surgical side. There was no significant difference in the first (p = 0.122) and second (p = 0.445) peak tibial compression forces during walking between the healthy and surgical sides. Conclusion: Patients with unilateral ACLR showed smaller tibial compression force on the surgical side than on the healthy side during jogging. The main reason for this may be the insufficient exertion of the rectus femoris and vastus medialis.

Dynamic knee stiffness during walking is increased in individuals with anterior cruciate ligament reconstruction

Individuals with anterior cruciate ligament (ACL) reconstruction often display abnormal gait mechanics reflective of a "stiff-knee" gait (i.e., reduced knee flexion angles and moments). However, dynamic knee stiffness, which is the dynamic relationship between the position of the knee and the moment acting on it, has not been directly examined during walking in individuals with ACL reconstruction. Here, we aimed to evaluate dynamic knee stiffness in the involved compared to the uninvolved limb during weight-acceptance and mid-stance phases of walking. Twenty-six individuals who underwent ACL reconstruction (Age: 20.2 ± 5.1 yrs., Time post-op: 7.2 ± 0.9 mo.) completed an overground walking assessment using a three-dimensional motion capture system and two force plates. Dynamic knee stiffness (Nm/°) was calculated as the slope of the regression line during weight-acceptance and midstance, obtained by plotting the sagittal plane knee angle versus knee moment. Paired t-tests with Bonferroni corrections were used to compare differences in dynamic stiffness, knee excursions, and moment ranges between limbs during both stance phases. Greater dynamic knee stiffness was found in the involved compared with the uninvolved limb during weight-acceptance and mid-stance (p < 0.01). Knee flexion and extension excursions were reduced in the involved limb during both weight-acceptance and mid-stance, respectively (p < 0.01). Sagittal plane knee moment ranges were not different between limbs during weight-acceptance (p = 0.1); however, the involved limb moment range was reduced relative to the uninvolved limb during mid-stance (p < 0.01). These results indicate that individuals with ACL reconstruction walk with a stiffer knee throughout stance, which may influence knee contact forces and could contribute to the high propensity for post-traumatic knee osteoarthritis development in this population.

Quadriceps Weakness is Associated with Neuroplastic Changes Within Specific Corticospinal Pathways and Brain Areas After Anterior Cruciate Ligament Reconstruction: Theoretical Utility of Motor Imagery-Based Brain-Computer Interface Technology for Rehabilitation

Persistent quadriceps weakness is a problematic sequela of anterior cruciate ligament reconstruction (ACLR). The purposes of this review are to summarize neuroplastic changes after ACL reconstruction; provide an overview of a promising interventions, motor imagery (MI), and its utility in muscle activation; and propose a framework using a brain-computer interface (BCI) to augment quadriceps activation. A literature review of neuroplastic changes, MI training, and BCI-MI technology in postoperative neuromuscular rehabilitation was conducted in PubMed, Embase, and Scopus. Combinations of the following search terms were used to identify articles: "quadriceps muscle," "neurofeedback," "biofeedback," "muscle activation," "motor learning," "anterior cruciate ligament," and "cortical plasticity." We found that ACLR disrupts sensory input from the quadriceps, which results in reduced sensitivity to electrochemical neuronal signals, an increase in central inhibition of neurons regulating quadriceps control and dampening of reflexive motor activity. MI training consists of visualizing an action, without physically engaging in muscle activity. Imagined motor output during MI training increases the sensitivity and conductivity of corticospinal tracts emerging from the primary motor cortex, which helps "exercise" the connections between the brain and target muscle tissues. Motor rehabilitation studies using BCI-MI technology have demonstrated increased excitability of the motor cortex, corticospinal tract, spinal motor neurons, and disinhibition of inhibitory interneurons. This technology has been validated and successfully applied in the recovery of atrophied neuromuscular pathways in stroke patients but has yet to be investigated in peripheral neuromuscular insults, such as ACL injury and reconstruction. Well-designed clinical studies may assess the impact of BCI on clinical outcomes and recovery time. Quadriceps weakness is associated with neuroplastic changes within specific corticospinal pathways and brain areas. BCI-MI shows strong potential for facilitating recovery of atrophied neuromuscular pathways after ACLR and may offer an innovative, multidisciplinary approach to orthopaedic care.

Level of Evidence

V, expert opinion.

Mechanical Factors Contributing to Altered Knee Extension Moment during Gait after ACL Reconstruction: A Longitudinal Analysis

PURPOSE

This study aimed to comprehensively examine the extent to which knee flexion angle at initial contact, peak knee flexion angle, and vertical ground reaction force (vGRF) contribute to knee extension moments during gait in individuals with anterior cruciate ligament (ACL) reconstruction.

METHODS

Overground gait biomechanics were evaluated in 26 participants with ACL reconstruction at three time points (about 2, 4, and 6 months after the surgery). Knee flexion angle at initial contact, peak knee flexion angle, peak vGRF, and peak knee extension moment were calculated for each limb during the early stance phase of gait for all three time points. A change score from baseline (time point 2 - time point 1 and time point 3 - time point 1) along with limb symmetry values (ACL - non-ACL limb values) was also calculated for these variables. Multiple linear regressions utilizing classical and Bayesian interference methods were used to determine the contribution of knee flexion angle and vGRF to knee extension moment during gait.

RESULTS

Peak knee flexion angle and peak vGRF positively contributed to knee extension moment during gait in both the reconstructed ( R2 = 0.767, P < 0.001) and nonreconstructed limbs ( R2 = 0.815, P < 0.001). Similar results were observed for the symmetry values ( R2 = 0.673, P < 0.001) and change scores ( R2 = 0.731-0.883; all P < 0.001), except that the changes in knee flexion angle at initial contact also contributed to the model using the change scores in the nonreconstructed limb (time point 2 - time point 1: R2 = 0.844, P < 0.001; time point 3 - time point 1: R2 = 0.883, P < 0.001). Bayesian regression evaluating the likelihood of these prediction models showed that there was decisive evidence favoring the alternative model over the null model (all Bayes factors >1000). Standardized β coefficients indicated that changes in knee flexion angle had a greater impact (>2×) on knee extension moments than vGRF at both time points in both limbs ( βvGRF = 0.204-0.309; βkneeflexion = 0.703-0.831).

CONCLUSIONS

The findings indicate that both knee flexion angle and peak vGRF positively contribute to altered knee extension moments during gait, but the contribution of knee flexion angle is much greater than vGRF. Therefore, treatment strategies targeting these variables may improve knee loading after ACL reconstruction.

Identification of Kinetic Abnormalities in Male Patients after Anterior Cruciate Ligament Deficiency Combined with Meniscal Injury: A Musculoskeletal Model Study of Lower Limbs during Jogging

There is little known about kinetic changes in anterior cruciate ligament deficiency (ACLD) combined with meniscal tears during jogging. Therefore, 29 male patients with injured ACLs and 15 healthy male volunteers were recruited for this study to investigate kinetic abnormalities in male patients after ACL deficiency combined with a meniscal injury during jogging. Based on experimental data measured by an optical tracking system, a subject-specific musculoskeletal model was employed to estimate the tibiofemoral joint kinetics during jogging. Between-limb and interpatient differences were compared by the analysis of variance. The results showed that decreased knee joint forces and moments of both legs in ACLD patients were detected during the stance phase compared to the control group. Meanwhile, compared with ACLD knees, significantly fewer contact forces and flexion moments in ACLD combined with lateral and medial meniscal injury groups were found at the mid-stance, and ACLD with medial meniscal injury group showed a lower axial moment in the loading response (p < 0.05). In conclusion, ACLD knees exhibit reduced tibiofemoral joint forces and moments during jogging when compared with control knees. A combination of meniscus injuries in the ACLD-affected side exhibited abnormal kinetic alterations at the loading response and mid-stance phase.

Effects of Neuromuscular Electrical Stimulation and Blood Flow Restriction in Rehabilitation after Anterior Cruciate Ligament Reconstruction

The present study aimed to examine and compare the effects of a rehabilitation exercise (RE) using neuromuscular electrical stimulation (NMES) and blood flow restriction (BFR) on muscle function and knee functional abilities in patients who underwent anterior cruciate ligament reconstruction (ACLR). A total of 45 patients who underwent ACLR (28.76 ± 0.8 years; 34 males and 11 females) were retrospectively divided into three groups: control (CON, n = 15), NMES (n = 15), and BFR (n = 15). All participants carried out the RE program for 60 min, thrice a week for 12 weeks. The Lysholm score, International Knee Documentation Committee (IKDC) subjective score, thigh circumference at 5 cm from the knee joint, Y-balance posterior medial, and lateral significantly increased in all groups via intervention (p < 0.05). However, NMES showed a higher thigh circumference at 15 cm from the knee joint than CON via intervention (p < 0.05), and the strength and endurance of quadriceps femoris and hamstrings and Y-balance anterior showed a significant increase via intervention in NMES and BFR compared with CON (p < 0.05). In conclusion, we confirmed that RE using NMES and BFR effectively enhances muscle function and balance in ACLR patients.

A Countermovement Jump for the Midterm Assessment of Force and Power Exertion After Anterior Cruciate Ligament Reconstruction

OBJECTIVE

The aim of this study was to assess force and power exertion during a countermovement jump after anterior cruciate ligament reconstruction using either semitendinosus and gracilis or bone-patellar tendon-bone graft.

DESIGN

One hundred-nineteen semitendinosus and gracilis and 146 bone-patellar tendon-bone participants performed a countermovement jump on two force platforms after 3 (T1) and 6-9 mos (T2) from surgery. Twenty-four healthy participants served as control group. Peak force of eccentric and concentric phases and peak power were obtained from the analysis of vertical components of the ground reaction forces. Asymmetry was quantified by means of limb symmetry index.

RESULTS

Eccentric peak force was significantly ( P < 0.05) lower than concentric peak force in both bone-patellar tendon-bone and semitendinosus and gracilis at T1 and T2. At T1, bone-patellar tendon-bone showed higher peak power, but lower limb symmetry index in eccentric and concentric compared with semitendinosus and gracilis. At T2, bone-patellar tendon-bone showed higher peak power than semitendinosus and gracilis, although there were no differences in limb symmetry index between the two groups, which however was significantly ( P < 0.05) lower in both groups when compared with control group.

CONCLUSIONS

Bone-patellar tendon-bone and semitendinosus and gracilis participants showed asymmetries in eccentric and concentric force during a countermovement jump. Bone-patellar tendon-bone showed greater asymmetries and a higher peak power respect to semitendinosus and gracilis participants.

Knee Strength Assessment and Clinical Evaluation Could Predict Return to Running after Anterior Cruciate Ligament Reconstruction Using Patellar Tendon Procedure

BACKGROUND AND OBJECTIVES

Muscle knee strength is a major parameter that allows return to running. Isokinetic strength parameters may predict return to running 4 months after ACLR using the bone-patellar-tendon-bone procedure.

MATERIALS AND METHODS

The isokinetic knee strength of 216 patients (24.5 ± 5 years) was measured 4 months after surgery, and progressive return to running was allowed. The effectiveness of return to running was reported at 6 months. Return to running prediction was established using multivariate logistic regression. Predictive parameters were presented with a ROC curve area to define the best cut-off, with sensibility (Se) and specificity (Sp).

RESULTS

A model was established, including the limb symmetry index (LSI), and 103 patients (47.6%) were able to run between the fourth and the sixth month after surgery. These patients presented significantly fewer knee complications, a better Lysholm score, a better Quadriceps and Hamstring LSI and better quadriceps strength reported for body weight on the operated limb. The best model was established including the Quadriceps and Hamstring LSI at 60°/s and the Lysholm score. The cut-off for Quadriceps LSI was 60% (ROC curve area: 0.847; Se: 77.5%; Sp: 77%), for Hamstring LSI 90% (ROC curve area: 0.716; Se: 65.7%; Sp: 60.2%) and for Lyshom score 97 points (ROC curve area: 0.691; Se: 65%; Sp: 66%).

CONCLUSION

Four months after ACLR using a bone-patellar-tendon-bone procedure, the Quadriceps and Hamstring LSI associated to the Lysholm score could help make the decision to allow return to running.

Influence of body mass index and anterior cruciate ligament reconstruction on gait biomechanics

Body mass index (BMI) and history of anterior cruciate ligament reconstruction (ACLR) independently influence gait biomechanics and knee osteoarthritis risk, but the interaction between these factors is unclear. The purpose of this study was to compare gait biomechanics between individuals with and without ACLR, and with and without overweight/obesity. We examined 104 individuals divided into four groups: with and without ACLR, and with low or high BMI (n = 26 per group). Three-dimensional gait biomechanics were evaluated at preferred speed. The peak vertical ground reaction force, knee flexion angle and excursion, external knee flexion moment, and external knee adduction moment were extracted for analysis. Gait features were compared between groups using 2 (with and without overweight/obesity) × 2 (with and without ACLR) analysis of variance. Primary findings indicated that those with ACLR and high BMI had a larger external knee adduction moment compared with those with low BMI and with (p = 0.004) and without ACLR (p = 0.005), and compared with those without ACLR and high BMI (p = 0.001). The main effects of ACLR and BMI group were found for the knee flexion moment, and those with ACLR and with high BMI had lower knee flexion moments compared with those without ACLR (p = 0.031) and with low BMI (p = 0.021), respectively. Data suggest that individuals with ACLR and high BMI may benefit from additional intervention targeting the knee adduction moment. Moreover, lower external knee flexion moments in those with high BMI and ACLR were consistent, but high BMI did not exacerbate deficits in the knee flexion moment in those with ACLR. [Correction added on 9 November 2022, after first online publication: In the preceding sentence, for clarity, the words "reductions in the lower" was removed from the initial sentence to read "Moreover, lower external knee flexion moments".].

Worse Tibiofemoral Cartilage Composition Is Associated with Insufficient Gait Kinetics After ACL Reconstruction

PURPOSE

Greater articular cartilage T1ρ magnetic resonance imaging relaxation times indicate less proteoglycan density and are linked to posttraumatic osteoarthritis development after anterior cruciate ligament reconstruction (ACLR). Although changes in T1ρ relaxation times are associated with gait biomechanics, it is unclear if excessive or insufficient knee joint loading is linked to greater T1ρ relaxation times 12 months post-ACLR. The purpose of this study was to compare external knee adduction (KAM) and flexion (KFM) moments in individuals after ACLR with high versus low tibiofemoral T1ρ relaxation profiles and uninjured controls.

METHODS

Gait biomechanics were collected in 26 uninjured controls (50% females; age, 22 ± 4 yr; body mass index, 23.9 ± 2.8 kg·m -2 ) and 26 individuals after ACLR (50% females; age, 22 ± 4 yr; body mass index, 24.2 ± 3.5 kg·m -2 ) at 6 and 12 months post-ACLR. ACLR-T1ρ High ( n = 9) and ACLR-T1ρ Low ( n = 17) groups were created based on 12-month post-ACLR T1ρ relaxation times using a k-means cluster analysis. Functional analyses of variance were used to compare KAM and KFM.

RESULTS

ACLR-T1ρ High exhibited lesser KAM than ACLR-T1ρ Low and uninjured controls 6 months post-ACLR. ACLR-T1ρ Low exhibited greater KAM than uninjured controls 6 and 12 months post-ACLR. KAM increased in ACLR-T1ρ High and decreased in ACLR-T1ρ Low between 6 and 12 months, both groups becoming more similar to uninjured controls. There were scant differences in KFM between ACLR-T1ρ High and ACLR-T1ρ Low 6 or 12 months post-ACLR, but both groups demonstrated lesser KFM compared with uninjured controls.

CONCLUSIONS

Associations between worse T1ρ profiles and increases in KAM may be driven by the normalization of KAM in individuals who initially exhibit insufficient KAM 6 months post-ACLR.

Kinetic energy absorption differences during drop jump between athletes with and without radiological signs of knee osteoarthritis: Two years post anterior cruciate ligament reconstruction

BACKGROUND

Patients demonstrate decreased knee loading and energy absorption after anterior cruciate ligament reconstruction (ACLR). This study aimed to determine the differences in the contribution of joints to the absorbed energy between athletes with and without radiological signs of knee OA 2 years after ACLR during drop jump (DJ) landing from 20, 30, and 40 cm.

METHODS

Forty-one (level I/II) athletes 2 years after ACLR participated in this cross-sectional study and completed motion analysis testing of DJ. Proportional contribution of the joints (foot, ankle, knee, and hip) to the absorbed energy were computed. Posterior-anterior bent-knee radiographs were completed and graded in the medial compartment of the reconstructed knee using the Kellgren-Lawrence (KL) system (OA group: KL ≥2; Non-OA group: KL<2) RESULTS: Thirteen (31.7%) athletes showed radiological signs of knee OA in the medial compartment. There was a significant joint-by-group-by-limb interaction for the contribution of joints to absorbed energy during DJ 40 cm (p ≤ 0.019) and a joint-by-group interaction for the contribution of joints during DJ 20 cm (p = 0.018). The OA group had a lower involved knee (p = 0.043) and higher involved hip contributions (p = 0.014) compared to the Non-OA group, and the non-involved knee (p = 0.007). While the Non-OA group had a lower involved ankle contribution (p = 0.045) compared to their non-involved ankle during DJ 40 cm. The OA group also had higher involved hip contribution than the Non-OA group (p = 0.010), lower involved knee (p = 0.002), and higher involved hip contribution than the non-involved limb during DJ 20 cm.

SIGNIFICANCE

The OA group may have adopted a compensatory pattern characterized by a decreased involved knee and increased involved hip to attenuate absorbed energy compared to the Non-OA group and their non-involved limb. The contribution of joints to the absorbed energy during DJ landing might be used as an assessment tool to identify patients with radiological signs of knee OA after ACLR.

Quadriceps strength symmetry predicts vertical ground reaction force symmetry during running in patients who have undergone ACL reconstruction

OBJECTIVE

To determine whether quadriceps strength symmetry can predict peak vertical ground reaction force (vGRF) running force symmetry in patients who have undergone ACL reconstruction (ACLR). We also sought to determine a cutoff for quadriceps strength symmetry to identify patients at risk for vGRF running asymmetry.

DESIGN

Retrospective cross-sectional.

SETTING

Clinical facility.

METHODS

Bilateral quadriceps strength and vGRF data during running were obtained from 79 patients 26-30 weeks post ACLR. Linear regression was used to determine if quadriceps strength symmetry predicted peak vGRF running force symmetry. Classification and regression tree (CART) analysis was used to determine the cutoff value for quadriceps strength symmetry to identify patients at risk for vGRF running asymmetry.

RESULTS

Increased quadriceps strength symmetry predicted increased vGRF running symmetry (R2 = 0.20). CART analysis revealed that patients with quadriceps strength symmetry less than or equal to 88% were at highest risk for vGRF running asymmetry (R2 = 26%).

CONCLUSION

Greater quadriceps strength symmetry is predictive of greater vGRF running force symmetry in patients who have undergone ACLR. This finding highlights the need for clinicians to consider the degree of quadriceps strength symmetry before initiating a return to running program.

Knee joint biomechanics during gait improve from 3 to 6 months after anterior cruciate ligament reconstruction

Gait alterations after anterior cruciate ligament reconstruction (ACLR) are commonly reported and have been linked to posttraumatic osteoarthritis development. While knee gait alterations have been studied at several time points after ACLR, little is known about how these biomechanical variables change earlier than 6 months after surgery, nor is much known about how they differ over the entire stance phase of gait. The purpose of this study was to examine knee gait biomechanical variables over their entire movement pattern through stance at both 3 and 6 months after ACLR and to study the progression of interlimb asymmetry between the two postoperative time points. Thirty-five individuals underwent motion analysis during overground walking 3 (3.2 ± 0.5) and 6 (6.4 ± 0.7) months after ACLR. Knee biomechanical variables were compared between limbs and across time points through 100% of stance using statistical parametric mapping; this included a 2 × 2 (Limb × Time) repeated measures analysis of variance and two-tailed t-tests. Smaller knee joint angles, moments, extensor forces, and medial compartment forces were present in the involved versus uninvolved limb. Interlimb asymmetries were present at both time points but were less prevalent at 6 months. The uninvolved limb's biomechanical variables stayed relatively consistent over time, while the involved limb's trended toward that of the uninvolved limb. Statement of Clinical Significance: Interventions to correct asymmetrical gait patterns after ACLR may need to occur early after surgery and may need to focus on multiple parts of stance phase.

Quadriceps Muscle Action and Association With Knee Joint Biomechanics in Individuals with Anterior Cruciate Ligament Reconstruction

Insufficient quadriceps force production and altered knee joint biomechanics after anterior cruciate ligament reconstruction (ACLR) may contribute to a heightened risk of osteoarthritis. Quadriceps muscle lengthening dynamics affect force production and knee joint loading; however, no study to our knowledge has quantified in vivo quadriceps dynamics during walking in individuals with ACLR or examined correlations with joint biomechanics. Our purpose was to quantify bilateral vastus lateralis (VL) fascicle length change and the association thereof with gait biomechanics during weight acceptance in individuals with ACLR. The authors hypothesized that ACLR limbs would exhibit more fascicle lengthening than contralateral limbs. The authors also hypothesized that ACLR limbs would exhibit positive correlations between VL fascicle lengthening and knee joint biomechanics during weight acceptance in walking. The authors quantified VL contractile dynamics via cine B-mode ultrasound imaging in 18 individuals with ACLR walking on an instrumented treadmill. In partial support of our hypothesis, ACLR limb VL fascicles activated without length change on average during weight acceptance while fascicle length on the contralateral limb decreased on average. The authors found a positive association between fascicle lengthening and increase in knee extensor moments in both limbs. Our results suggest that examining quadriceps muscle dynamics may elucidate underlying mechanisms relevant to osteoarthritis.

Pre-operative knee extensor and flexor torque after secondary ACL rupture: a comparative retrospective analysis

Background

Secondary anterior cruciate ligament (ACL) ruptures are a relevant clinical concern after surgical treatment of a primary ACL rupture. However, there is a lack of scientific evidence related to the role of muscle strength prior to revision surgery in a second ACL rupture. The aim of this study was to assess differences in knee extensor and flexor strength in patients before primary and secondary ACL reconstruction compared to healthy controls.

Methods

In total, n = 69 age, weight and sex matched individuals were included in the study: n = 23 patients with isolated primary ACL rupture, n = 23 with secondary ACL rupture, and n = 23 matched healthy controls. Maximal isokinetic knee extension and flexion torque normalized to body mass was assessed for both legs.

Results

For patients with secondary ACL ruptures, torques were reduced in the non-injured (extension: 1.94 Nm/kg vs. 2.46 Nm/kg, p < 0.05, flexion: 1.25 Nm/kg vs. 1.59 Nm/kg, p < 0.05) and the injured leg (extension: 1.70 Nm/kg vs. 2.46 Nm/kg, p < 0.05, flexion: 1.14 Nm/kg vs. 1.59 Nm/kg, p < 0.05) compared to healthy controls. For patients with a primary ACL rupture torques were reduced in the non-injured (extension: 1.92 Nm/kg vs. 2.46 Nm/kg, p < 0.05, flexion: 1.24 Nm/kg vs. 1.59 Nm/kg, p < 0.05) and the injured leg (extension: 1.38 Nm/kg vs. 2.46 Nm/kg, p < 0.05, flexion: 1.01 Nm/kg vs. 1.59 Nm/kg, p < 0.05) compared to healthy controls. There were no differences between patients with primary and secondary ruptures, except of the knee extension on the injured leg showing higher values after a secondary ACL rupture (1.38 Nm/kg vs. 1.70 Nm/kg, p < 0.05).

Conclusions

The findings indicate that maximal knee torques were significantly reduced in patients with primary and secondary ACL ruptures before surgical reconstruction for the non-injured and injured leg as compared to healthy controls. Further investigations are needed to assess strength abilities before and after a second revision within a prospective design.

Relevant Strength Parameters to Allow Return to Running after Primary Anterior Cruciate Ligament Reconstruction with Hamstring Tendon Autograft

After anterior cruciate ligament reconstruction (ACLR), a progressive process is followed from rehabilitation to the return to sport including a crucial step known as the return to running. Return to running (RTR) can be predicted by an isokinetic knee strength assessment at 4 months post-surgery. All patients who had primarily undergone ACLR with a hamstring autograft procedure between 2010 and 2020 were included in this study. Four months after surgery, patients were evaluated using an isokinetic knee strength test. Patients were monitored until the 6th month post-surgery to see if they had returned to running. Comparisons were carried out between the two groups—the RTR and the no-RTR. A multivariate logistic regression analysis was used to predict the RTR status from explicative parameters. Receiver Operating Characteristic (ROC) curves were established to identify cutoffs with their characteristics. A total of 413 patients were included and 63.2% returned to running at 4 months post-surgery. The mean Lysholm score, knee complication rate, and isokinetic parameters were statistically different between both groups. Using a multivariate logistic regression model and ROC curves, the best isokinetic parameter to assist with the decision to allow an RTR was the quadriceps limb symmetry index at 60°/s with a cutoff of 65%. The hamstring LSI at 180°/s could be added (cutoff of 80%) to slightly increase the prediction of an RTR. Quadriceps strength normalized to body weight at 60°/s is a useful parameter (cutoff: 1.60 Nm/kg) but measurements on both sides are necessary. Isokinetic parameters are objective parameters to allow a return to running at 4 months after ACLR with a hamstring procedure.

Effect of Time After Injury on Tibiofemoral Joint Kinematics in Anterior Cruciate Ligament-Deficient Knees During Gait

Background:

Anterior cruciate ligament (ACL) injury can lead to changes in tibiofemoral kinematics during gait, but the detailed short-term kinematic changes after ACL injury are still unknown.

Purpose:

To measure tibiofemoral kinematics during gait in ACL-deficient (ACLD) knees over time after ACL injury.

Study Design:

Controlled laboratory study.

Methods:

The authors categorized 76 patients with unilateral ACLD knees into 4 groups based on the time from injury: <3 months (group 1), 3 to 6 months (group 2), >6 to 12 months (group 3), and >12 months (group 4). The controls were 20 participants with ACL-intact knees. Changes in the knee kinematics and range of motion during gait were compared among ACLD groups and those with ACL-intact knees.

Results:

Compared with controls, the range of motion of flexion in group 1 was significantly lower (6°; P = .033), and the mean knee flexion was significantly increased (0.7°-3.4°) in groups 1 to 4 (all P ≤ .004). There was more internal tibial rotation (2.9°-4.3°) in group 1 and 2, and more anterior tibial translation (4.3 mm) in group 1 during the stance or swing phases than in controls (P ≤ .049 for all). The mean internal tibial rotation and anterior tibial translation significantly decreased from group 1 to group 4 (P < .001 for both). Compared with controls, the mean medial tibial translation was significantly greater (1.2-2.5 mm) in all groups, and more medial tibial translations (2.4-3.7 mm) were observed during the stance phase in groups 1, 3, and 4 (P ≤ .047 for all).

Conclusion:

ACLD knees displayed a motion impairment walking strategy within 3 months, and a higher-flexion walking strategy increased with time after injury. Excessive anterior translation and internal rotation of the tibia tended to return to normal, while excessive medial translation of the tibia increased in ACLD knees after 6 months postinjury. These results may provide new insight into the compensatory mechanisms and risk factors for premature osteoarthritis in ACLD knees.

Anterior cruciate ligament reconstruction using quadriceps tendon autograft is a viable option for small-statured female patients

PURPOSE

The choice of graft for anterior cruciate ligament (ACL) reconstruction remains controversial. The quadriceps tendon (QT) autograft is a good alternative for ACL reconstruction. However, concerns regarding its use in short-statured patients, related to donor site morbidity, anterior knee pain, or loss of muscle strength remain. This study aimed to compare muscle strength and morbidity between patients with short and normal statures following ACL reconstruction with a QT autograft.

METHODS

A total of 73 female patients (mean age, 33.8 ± 11.5 years) who underwent primary ACL reconstruction between 2016 and 2019 were included. Patients were categorized into two groups: group S, with a height ≤ 163 cm, and group L, with a height > 163 cm. Muscle strength, harvesting site morbidity, and ACL-return to sport after injury scale (ACL-RSI) were evaluated, with a mean timing of the follow-up of 9.0 ± 2.3 months.

RESULTS

The mean quadriceps strength for the isokinetic measurements at 60° and 240° was 65.0% and 74.0% in group S, respectively, and 70.0% and 75.7% in group L, respectively. There was no significant difference in the postoperative muscle strength or mean ACL-RSI (group S, 70.0; group L, 65.9) between the groups. No donor site morbidity was observed in either group.

CONCLUSION

Muscle strength recovery, morbidity, and readiness to return to sports were similar in both groups, which supports the possibility of QT autografts for patients with a small stature. The results of this study may provide useful information for surgeons who are hesitant to perform QT autografts because of patient physique.

LEVEL OF EVIDENCE

IV.

Functional Resistance Training Differentially Alters Gait Kinetics After Anterior Cruciate Ligament Reconstruction: A Pilot Study

BACKGROUND

Quadriceps weakness is common after anterior cruciate ligament (ACL) reconstruction and can alter gait mechanics. Functional resistance training (FRT) is a novel approach to retraining strength after injury, but it is unclear how it alters gait mechanics. Therefore, we tested how 3 different types of FRT devices: a knee brace resisting extension (unidirectional brace), a knee brace resisting extension and flexion (bidirectional brace), and an elastic band pulling backwards on the ankle (elastic band)-acutely alter gait kinetics in this population.

HYPOTHESIS

The type of FRT device will affect ground-reaction forces (GRFs) during and after the training. Specifically, the uni- and bidirectional braces will increase GRFs when compared with the elastic band.

STUDY DESIGN

Crossover study.

LEVEL OF EVIDENCE

Level 2.

METHODS

A total of 15 individuals with ACL reconstruction received FRT with each device over 3 separate randomized sessions. During training, participants walked on a treadmill while performing a tracking task with visual feedback. Sessions contained 5 training trials (180 seconds each) with rest between. Vertical and anterior-posterior GRFs were assessed on the ACL-reconstructed leg before, during, and after training. Changes in GRFs were compared across devices using 1-dimensional statistical parametric mapping.

RESULTS

Resistance applied via bidirectional brace acutely increased gait kinetics during terminal stance/pre-swing (ie, push-off), while resistance applied via elastic band acutely increased gait kinetics during initial contact/loading (ie, braking). Both braces behaved similarly, but the unidirectional brace was less effective for increasing push-off GRFs.

CONCLUSION

FRT after ACL reconstruction can acutely alter gait kinetics during training. Devices can be applied to selectively alter gait kinetics. However, the long-term effects of FRT after ACL reconstruction with these devices are still unknown.

CLINICAL RELEVANCE

FRT may be applied to alter gait kinetics of the involved limb after ACL reconstruction, depending on the device used.