Quadriceps weakness associates with greater T1ρ relaxation time in the medial femoral articular cartilage 6 months following anterior cruciate ligament reconstruction

Beyond weakness: Exploring intramuscular fat and quadriceps atrophy in ACLR recovery

Muscle weakness following anterior cruciate ligament reconstruction (ACLR) increases the risk of posttraumatic osteoarthritis (OA). However, focusing solely on muscle weakness overlooks other aspects like muscle composition, which could hinder strength recovery. Intramuscular fat is a non-contractile element linked to joint degeneration in idiopathic OA, but its role post-ACLR has not been thoroughly investigated. To bridge this gap, we aimed to characterize quadriceps volume and intramuscular fat in participants with ACLR (male/female = 15/9, age = 22.8 ± 3.6 years, body mass index [BMI] = 23.2 ± 1.9, time since surgery = 3.3 ± 0.9 years) and in controls (male/female = 14/10, age = 22.0 ± 3.1 years, BMI = 23.3 ± 2.6) while also exploring the associations between intramuscular fat and muscle volume with isometric strength. Linear mixed effects models assessed (I) muscle volume, (II) intramuscular fat, and (III) strength between limbs (ACLR vs. contralateral vs. control). Regression analyses were run to determine if intramuscular fat or volume were associated with quadriceps strength. The ACLR limb was 8%-11% smaller than the contralateral limb (p < 0.05). No between-limb differences in intramuscular fat were observed (p 0.091-0.997). Muscle volume but not intramuscular fat was associated with strength in the ACLR and control limbs (p < 0.001-0.002). We demonstrate that intramuscular fat does not appear to be an additional source of quadriceps dysfunction following ACLR and that muscle size only explains some of the variance in muscle strength.

Association Between Knee Flexor Strength and Preservation of the Tibial Attachment of the Sartorial Fascia During Hamstring Tendon Harvest

Background

During anterior cruciate ligament (ACL) reconstruction, there are various autograft options. Donor-site morbidity is an important consideration while deciding the type of the autograft. Gracilis and semitendinosus autografts are commonly used in ACL reconstruction, resulting in weakness of the hamstring muscle.

Hypothesis

We hypothesized that if we preserved the tibial insertion site of the sartorial fascia (SF) during hamstring tendon harvest, there would be better recovery of knee flexor strength.

Study Design

Case-control study; Level of evidence, 3.

Methods

In this retrospective study, 34 patients (aged 20-59 years) underwent ACL reconstruction using hamstring tendon autograft with 2 different incision techniques on the SF. The tibial attachment site of the SF was preserved in 17 patients. The insertion site of the muscle was incised transversely in 17 patients. The follow-up duration was ≥2 years. Patients were recalled to the institute for examination and muscle strength assessment. The results were compared between the groups in terms of flexor and extensor knee isokinetic muscle strength at 60 and 180 deg/s.

Results

There was no statistical difference between the groups in terms of age, sex, or body mass index. When compared with patients whose SF attachment site was incised, patients with a preserved SF tibial insertion were found to have a higher flexion peak torque at the angular speed of 180 deg/s (P < 002). No statistically significant difference was noted at 60 deg/s.

Conclusion

During collection of gracilis and semitendinosus autografts, preserving the SF tibial attachment site was associated with better knee flexion peak torque.

Quantitative Magnetic Resonance Imaging of Lateral Compartment Articular Cartilage After Lateral Extra-articular Tenodesis

BACKGROUND

Concerns have arisen that anterior cruciate ligament reconstruction (ACLR) with lateral extra-articular tenodesis (LET) may accelerate the development of posttraumatic osteoarthritis in the lateral compartment of the knee.

PURPOSE/HYPOTHESIS

The purpose of this study was to evaluate whether the augmentation of ACLR with LET affects the quality of lateral compartment articular cartilage on magnetic resonance imaging (MRI) at 2 years postoperatively. We hypothesized that there would be no difference in T1rho and T2 relaxation times when comparing ACLR alone with ACLR + LET.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

A consecutive subgroup of patients at the Fowler Kennedy Sport Medicine Clinic participating in the STABILITY 1 Study underwent bilateral 3-T MRI at 2 years after surgery. The primary outcome was T1rho and T2 relaxation times. Articular cartilage in the lateral compartment was manually segmented into 3 regions of the tibia (lateral tibia [LT]-1 to LT-3) and 5 regions of the femur (lateral femoral condyle [LFC]-1 to LFC-5). Analysis of covariance was used to compare relaxation times between groups, adjusted for lateral meniscal tears and treatment, cartilage and bone marrow lesions, contralateral relaxation times, and time since surgery. Semiquantitative MRI scores according to the Anterior Cruciate Ligament OsteoArthritis Score were compared between groups. Correlations were used to determine the association between secondary outcomes (including results of the International Knee Documentation Committee score, Knee injury and Osteoarthritis Outcome Score, Lower Extremity Functional Scale, 4-Item Pain Intensity Measure, hop tests, and isokinetic quadriceps and hamstring strength tests) and cartilage relaxation.

RESULTS

A total of 95 participants (44 ACLR alone, 51 ACLR + LET) with a mean age of 18.8 years (61.1% female [58/95]) underwent 2-year MRI (range, 20-36 months). T1rho relaxation times were significantly elevated for the ACLR + LET group in LT-1 (37.3 ± 0.7 ms vs 34.1 ± 0.8 ms, respectively; P = .005) and LFC-2 (43.9 ± 0.9 ms vs 40.2 ± 1.0 ms, respectively; P = .008) compared with the ACLR alone group. T2 relaxation times were significantly elevated for the ACLR + LET group in LFC-1 (51.2 ± 0.7 ms vs 49.1 ± 0.7 ms, respectively; P = .03) and LFC-4 (45.9 ± 0.5 ms vs 44.2 ± 0.6 ms, respectively; P = .04) compared with the ACLR alone group. All effect sizes were small to medium. There was no difference in Anterior Cruciate Ligament OsteoArthritis Scores between groups (P = .99). Weak negative associations (rs = -0.27 to -0.22; P < .05) were found between relaxation times and quadriceps and hamstring strength in the anterolateral knee, while all other correlations were nonsignificant (P > .05).

CONCLUSION

Increased relaxation times demonstrating small to medium effect sizes suggested early biochemical changes in articular cartilage of the anterolateral compartment in the ACLR + LET group compared with the ACLR alone group. Further evidence and long-term follow-up are needed to better understand the association between these results and the potential risk of the development of osteoarthritis in our patient cohort.

Follow-up Treatment after Cartilage Therapy of the Knee Joint - a Recommendation of the DGOU Clinical Tissue Regeneration Working Group

The first follow-up treatment recommendation from the DGOU's Clinical Tissue Regeneration working group dates back to 2012. New scientific evidence and changed framework conditions made it necessary to update the follow-up treatment recommendations after cartilage therapy.As part of a multi-stage member survey, a consensus was reached which, together with the scientific evidence, provides the basis for the present follow-up treatment recommendation.The decisive criterion for follow-up treatment is still the defect localisation. A distinction is made between femorotibial and patellofemoral defects. In addition, further criteria regarding cartilage defects are now also taken into account (stable cartilage edge, location outside the main stress zone) and the different methods of cartilage therapy (e. g. osteochondral transplantation, minced cartilage) are discussed.The present updated recommendation includes different aspects of follow-up treatment, starting with early perioperative management through to sports clearance and resumption of contact sports after cartilage therapy has taken place.

Multiparametric MRI of Knees in Collegiate Basketball Players: Associations With Morphological Abnormalities and Functional Deficits

Background

Rates of cartilage degeneration in asymptomatic elite basketball players are significantly higher compared with the general population due to excessive loads on the knee. Compositional quantitative magnetic resonance imaging (qMRI) techniques can identify local biochemical changes of macromolecules observed in cartilage degeneration.

Purpose/Hypothesis

The purpose of this study was to utilize multiparametric qMRI to (1) quantify how T1ρ and T2 relaxation times differ based on the presence of anatomic abnormalities and (2) correlate T1ρ and T2 with self-reported functional deficits. It was hypothesized that prolonged relaxation times will be associated with knees with MRI-graded abnormalities and knees belonging to basketball players with greater self-reported functional deficits.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

A total of 75 knees from National Collegiate Athletic Association Division I basketball players (40 female, 35 male) were included in this multicenter study. All players completed the Knee injury and Osteoarthritis Outcome Score (KOOS) and had bilateral knee MRI scans taken. T1ρ and T2 were calculated on a voxel-by-voxel basis. The cartilage surfaces were segmented into 6 compartments: lateral femoral condyle, lateral tibia, medial femoral condyle, medial tibia (MT), patella (PAT), and trochlea (TRO). Lesions from the MRI scans were graded for imaging abnormalities, and statistical parametric mapping was performed to study cross-sectional differences based on MRI scan grading of anatomic knee abnormalities. Pearson partial correlations between relaxation times and KOOS subscore values were computed, obtaining r value statistical parametric mappings and P value clusters.

Results

Knees without patellar tendinosis displayed significantly higher T1ρ in the PAT compared with those with patellar tendinosis (average percentage difference, 10.4%; P = .02). Significant prolongation of T1ρ was observed in the MT, TRO, and PAT of knees without compared with those with quadriceps tendinosis (average percentage difference, 12.7%, 13.3%, and 13.4%, respectively; P ≤ .05). A weak correlation was found between the KOOS-Symptoms subscale values and T1ρ/T2.

Conclusion

Certain tissues that bear the brunt of impact developed tendinosis but spared cartilage degeneration. Whereas participants reported minimal functional deficits, their high-impact activities resulted in structural damage that may lead to osteoarthritis after their collegiate careers.

Hamstrings vibration reduces tibiofemoral compressive force following anterior cruciate ligament reconstruction

Individuals who have undergone anterior cruciate ligament reconstruction (ACLR) are at greater risk of developing knee osteoarthritis (OA). This elevated risk of knee OA is associated with high tibiofemoral (TF) compressive force, due to a combination of low knee flexion angles and increased co-contraction of the hamstrings and quadriceps during limb loading. Prolonged vibration of the hamstrings fatigues the intrafusal muscle fibers, which reduces autonomic reflexive excitation of the hamstrings and alleviates reciprocal inhibition to the quadriceps. The aim of this study was to examine the effect of prolonged hamstrings vibration on TF compressive force in individuals who have undergone ACL reconstruction. Fourteen participants with unilateral ACLR and 14 participants without knee injury performed a single-leg drop-land task before and after prolonged (20 min) vibration of the hamstrings. Peak TF compressive force, knee flexion angle, and hamstrings/quadriceps co-contraction were calculated during the deceleration phase of the drop-land task before and after vibration. The ACLR group experienced an 18% decrease in TF compressive force, a 32% increase in knee flexion angle, and a 38% decrease in hamstrings/quadriceps co-contraction after hamstrings vibration. There was no difference in any of the parameters in the noninjured group after vibration. These data suggest that acute prolonged hamstrings vibration has the potential to mitigate TF compressive force, which may protect the knee joint in the long term. Clinical significance: The results of this research are expected to lead to improved clinical care for ACLR patients because it holds promise for mitigating altered joint mechanics and perhaps slowing down the onset of posttraumatic knee osteoarthritis.

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.

Preclinical tendon and ligament models: Beyond the 3Rs (replacement, reduction, and refinement) to 5W1H (why, who, what, where, when, how)

Several tendon and ligament animal models were presented at the 2022 Orthopaedic Research Society Tendon Section Conference held at the University of Pennsylvania, May 5 to 7, 2022. A key objective of the breakout sessions at this meeting was to develop guidelines for the field, including for preclinical tendon and ligament animal models. This review summarizes the perspectives of experts for eight surgical small and large animal models of rotator cuff tear, flexor tendon transection, anterior cruciate ligament tear, and Achilles tendon injury using the framework: "Why, Who, What, Where, When, and How" (5W1H). A notable conclusion is that the perfect tendon model does not exist; there is no single gold standard animal model that represents the totality of tendon and ligament disease. Each model has advantages and disadvantages and should be carefully considered in light of the specific research question. There are also circumstances when an animal model is not the best approach. The wide variety of tendon and ligament pathologies necessitates choices between small and large animal models, different anatomic sites, and a range of factors associated with each model during the planning phase. Attendees agreed on some guiding principles including: providing clear justification for the model selected, providing animal model details at publication, encouraging sharing of protocols and expertise, improving training of research personnel, and considering greater collaboration with veterinarians. A clear path for translating from animal models to clinical practice was also considered as a critical next step for accelerating progress in the tendon and ligament field.

Evidence Review for Preventing Osteoarthritis After an Anterior Cruciate Ligament Injury: An Osteoarthritis Action Alliance Consensus Statement

CONTEXT

The Osteoarthritis Action Alliance formed a secondary prevention task group to develop a consensus on secondary prevention recommendations to reduce the risk of osteoarthritis after a knee injury.

OBJECTIVE

Our goal was to provide clinicians with secondary prevention recommendations that are intended to reduce the risk of osteoarthritis after a person has sustained an anterior cruciate ligament injury. Specifically, this manuscript describes our methods, literature reviews, and dissenting opinions to elaborate on the rationale for our recommendations and to identify critical gaps.

DESIGN

Consensus process.

SETTING

Virtual video conference calls and online voting.

PATIENTS OR OTHER PARTICIPANTS

The Secondary Prevention Task Group consisted of 29 members from various clinical backgrounds.

MAIN OUTCOME MEASURE(S)

The group initially convened online in August 2020 to discuss the target population, goals, and key topics. After a second call, the task group divided into 9 subgroups to draft the recommendations and supportive text for crucial content areas. Twenty-one members completed 2 rounds of voting and revising the recommendations and supportive text between February and April 2021. A virtual meeting was held to review the wording of the recommendations and obtain final votes. We defined consensus as >80% of voting members supporting a proposed recommendation.

RESULTS

The group achieved consensus on 15 of 16 recommendations. The recommendations address patient education, exercise and rehabilitation, psychological skills training, graded-exposure therapy, cognitive-behavioral counseling (lacked consensus), outcomes to monitor, secondary injury prevention, system-level social support, leveraging technology, and coordinated care models.

CONCLUSIONS

This consensus statement reflects information synthesized from an interdisciplinary group of experts based on the best available evidence from the literature or personal experience. We hope this document raises awareness among clinicians and researchers to take steps to mitigate the risk of osteoarthritis after an anterior cruciate ligament injury.

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.

Primary surgery versus primary rehabilitation for treating anterior cruciate ligament injuries: a living systematic review and meta-analysis

OBJECTIVE

Compare the effectiveness of primarily surgical versus primarily rehabilitative management for anterior cruciate ligament (ACL) rupture.

DESIGN

Living systematic review and meta-analysis.

DATA SOURCES

Six databases, six trial registries and prior systematic reviews. Forward and backward citation tracking was employed.

ELIGIBILITY CRITERIA

Randomised controlled trials that compared primary reconstructive surgery and primary rehabilitative treatment with or without optional reconstructive surgery.

DATA SYNTHESIS

Bayesian random effects meta-analysis with empirical priors for the OR and standardised mean difference and 95% credible intervals (CrI), Cochrane RoB2, and the Grading of Recommendations Assessment, Development and Evaluation approach to judge the certainty of evidence.

RESULTS

Of 9514 records, 9 reports of three studies (320 participants in total) were included. No clinically important differences were observed at any follow-up for self-reported knee function (low to very low certainty of evidence). For radiological knee osteoarthritis, we found no effect at very low certainty of evidence in the long term (OR (95% CrI): 1.45 (0.30 to 5.17), two studies). Meniscal damage showed no effect at low certainty of evidence (OR: 0.85 (95% CI 0.45 to 1.62); one study) in the long term. No differences were observed between treatments for any other secondary outcome. Three ongoing randomised controlled trials were identified.

CONCLUSIONS

There is low to very low certainty of evidence that primary rehabilitation with optional surgical reconstruction results in similar outcome measures as early surgical reconstruction for ACL rupture. The findings challenge a historical paradigm that anatomic instability should be addressed with primary surgical stabilisation to provide optimal outcomes.

PROSPERO REGISTRATION NUMBER

CRD42021256537.

Quadriceps muscle strength at 2 years following anterior cruciate ligament reconstruction is associated with tibiofemoral joint cartilage volume

PURPOSE

Quadriceps strength deficits following anterior cruciate ligament reconstruction (ACLR) are linked to altered lower extremity biomechanics, tibiofemoral joint (TFJ) space narrowing and cartilage composition changes. It is unknown, however, if quadriceps strength is associated with cartilage volume in the early years following ACLR prior to the onset of posttraumatic osteoarthritis (OA) development. The purpose of this cross-sectional study was to examine the relationship between quadriceps muscle strength (peak and across the functional range of knee flexion) and cartilage volume at ~ 2 years following ACLR and determine the influence of concomitant meniscal pathology.

METHODS

The involved limb of 51 ACLR participants (31 isolated ACLR; 20 combined meniscal pathology) aged 18-40 years were tested at 2.4 ± 0.4 years post-surgery. Isokinetic knee extension torque generated in 10° intervals between 60° and 10° knee flexion (i.e. 60°-50°, 50°-40°, 40°-30°, 30°-20°, 20°-10°) together with peak extension torque were measured. Tibial and patellar cartilage volumes were measured using magnetic resonance imaging (MRI). The relationships between peak and angle-specific knee extension torque and MRI-derived cartilage volumes were evaluated using multiple linear regression.

RESULTS

In ACLR participants with and without meniscal pathology, higher knee extension torques at 60°-50° and 50°-40° knee flexion were negatively associated with medial tibial cartilage volume (p < 0.05). No significant associations were identified between peak concentric or angle-specific knee extension torques and patellar cartilage volume.

CONCLUSION

Higher quadriceps strength at knee flexion angles of 60°-40° was associated with lower cartilage volume on the medial tibia ~ 2 years following ACLR with and without concomitant meniscal injury. Regaining quadriceps strength across important functional ranges of knee flexion after ACLR may reduce the likelihood of developing early TFJ cartilage degenerative changes.

LEVEL OF EVIDENCE

III.

Effects of Hip Joint Angle on Quadriceps Recruitment Pattern During Knee Extension in Healthy Individuals: Analysis by Ultrasound-Based Shear-Wave Elastography

Purposes: To detect the effects of hip joint position on the quadriceps recruitment pattern of different resistance levels of rectus femoris (RF), vastus intermedius (VI), vastus lateralis (VL), and vastus medialis obliquus (VMO) in healthy people during knee extension.

Methods: Twenty healthy females performed isometric knee extension contractions at 0, 10, 20, and 30% of maximal voluntary isometric contraction (MVIC) with a 90° and 0° hip angle. Ultrasound shear-wave elastography was used to evaluate the shear elastic modulus of RF, VI, VL, and VMO during resting and contraction states.

Results: At resting state, stiffness of RF was about 50% higher at 0° compared with at 90° of the hip (p < 0.01). There were significant differences in comparisons between 0 and 10% MVIC, 10 and 20% MVIC, and 20 and 30% MVIC in the four muscles, except that there was no significant difference between 20 and 30% MVIC for RF. There was a significant positive correlation between muscle stiffness and resistance level (r = 0.78–0.94, p < 0.001).

Conclusions: Hip joint position had effects on the quadriceps recruitment pattern of different resistance levels in healthy people during knee extension.

Arthrogenic Muscle Inhibition Following Anterior Cruciate Ligament Injury

Arthrogenic muscle inhibition (AMI) is a common impairment in individuals who sustain an anterior cruciate ligament (ACL) injury. The AMI causes decreased muscle activation, which impairs muscle strength, leading to aberrant movement biomechanics. The AMI is often resistant to traditional rehabilitation techniques, which leads to persistent neuromuscular deficits following ACL reconstruction. To better treat AMI following ACL injury and ACL reconstruction, it is important to understand the specific neural pathways involved in AMI pathogenesis, as well as the changes in muscle function that may impact movement biomechanics and long-term structural alterations to joint tissue. Overall, AMI is a critical factor that limits optimal rehabilitation outcomes following ACL injury and ACL reconstruction. This review discusses the current understanding of the: (1) neural pathways involved in the AMI pathogenesis following ACL injury; (2) consequence of AMI on muscle function, joint biomechanics, and patient function; and (3) development of posttraumatic osteoarthritis. Finally, the authors review the evidence for interventions specifically used to target AMI following ACL injury.

Loading during Midstance of Gait Is Associated with Magnetic Resonance Imaging of Cartilage Composition Following Anterior Cruciate Ligament Reconstruction

OBJECTIVE

A complex association exists between aberrant gait biomechanics and posttraumatic knee osteoarthritis (PTOA) development. Previous research has primarily focused on the link between peak loading during the loading phase of stance and joint tissue changes following anterior cruciate ligament reconstruction (ACLR). However, the associations between loading and cartilage composition at other portions of stance, including midstance and late stance, is unclear. The objective of this study was to explore associations between vertical ground reaction force (vGRF) at each 1% increment of stance phase and tibiofemoral articular cartilage magnetic resonance imaging (MRI) T1ρ relaxation times following ACLR.

DESIGN

Twenty-three individuals (47.82% female, 22.1 ±4.1 years old) with unilateral ACLR participated in a gait assessment and T1ρ MRI collection at 12.25 ± 0.61 months post-ACLR. T1ρ relaxation times were calculated for the articular cartilage of the weightbearing medial and lateral femoral (MFC, LFC) and tibial (MTC, LTC) condyles. Separate bivariate, Pearson product moment correlation coefficients (r) were used to estimate strength of associations between T1ρ MRI relaxation times in the medial and lateral tibiofemoral articular cartilage with vGRF across the entire stance phase.

RESULTS

Greater vGRF during midstance (46%-56% of stance phase) was associated with greater T1ρ MRI relaxation times in the MFC (r ranging between 0.43 and 0.46).

CONCLUSIONS

Biomechanical gait profiles that include greater vGRF during midstance are associated with MRI estimates of lesser proteoglycan density in the MFC. Inability to unload the ACLR limb during midstance may be linked to joint tissue changes associated with PTOA development.

Return-to-sport quadriceps strength symmetry impacts 5-year cartilage integrity after anterior cruciate ligament reconstruction: A preliminary analysis

Quadriceps femoris strength asymmetry at the time of return to sports participation after anterior cruciate ligament (ACL) reconstruction contributes to worse function and asymmetric landing patterns, but the impact on longitudinal outcomes is not known. This study determined if young athletes after ACL reconstruction with quadriceps femoris strength asymmetry at a return to sports clearance would demonstrate markers of knee cartilage degeneration 5 years later compared to those with symmetric quadriceps femoris strength at return to sports. Participants (n = 27) were enrolled at the time of medical clearance for sports participation (baseline testing) and followed for 5 years. At baseline, quadriceps femoris strength was measured bilaterally and a limb symmetry index was used to divide the cohort into two groups: return to sport clearance with high quadriceps femoris strength (RTS-HQ; limb symmetry index ≥ 90%) and return to sport clearance with low quadriceps femoris strength (RTS-LQ; limb symmetry index < 85%). At 5 years post-baseline, quantitative magnetic resonance imaging (T2 relaxation times (ms): involved knee medial/lateral femoral condyle and tibial plateau) data were collected. Group differences were evaluated with independent samples t tests. At 5 years post-return to sports, the RTS-LQ strength group (n = 14) demonstrated elevated T2 relaxation times at the anterior region of the lateral femoral condyle compared to the RTS-HQ strength group (n = 13). Clinical Significance: Just over 50% of this cohort was cleared for sports participation with involved limb quadriceps femoris strength deficits that may contribute to early markers of knee cartilage degeneration within the subsequent 5 years.

Establishing an in vitro model of MR-T1ρ imaging technology to quantify nucleus pulposus tissue proteoglycans: a preliminary study

Background

The aim of the present study was to construct an in vitro model of degenerated nucleus pulposus with different combinations of biochemical components, and to find an in vitro model for the early degeneration of nucleus pulposus suitable for the detection of magnetic resonance T1rho (MR-T1ρ) sequence for the early diagnosis of degeneration of lumbar intervertebral disc.

Methods

The proteoglycan concentration gradient in the first experimental group was 5%, with a concentration range of 7 samples in vitro models from 5% to 35%. The second experimental group had 15 samples with a 1% concentration gradient of proteoglycan (range, 10–24%), with a higher water content compared with the first group. The third experimental group contained 20 samples with a concentration gradient of 1% proteoglycan (range, 10–29%), with 75% water content. All of the in vitro models were scanned using a 3.0T GE MR. To analyze the correlation between the proteoglycan content of the in vitro model and the T1ρ value, we investigated the feasibility and stability of modeling.

Results

There was no correlation between the in vitro model proteoglycan concentration and T1ρ value in the first experimental group; however, there was a significant negative correlation between the proteoglycan concentration and T1ρ value in the second experimental group (Y=–3.02X+131.8, R²=0.852, P<0.05). In the third experimental group, the proteoglycan concentration was significantly positively correlated with T1ρ value (Y=3.05X+11.99, R²=0.834, P<0.05). The comparison of the T1ρ values in the third experimental group before and 3 months after yielded an intraclass correlation coefficient value of 0.980, indicating that the biochemical components in the third experimental group were still stable after 3 months of storage. The slope of the regression equation between the Pfirrmann grading and T1ρ value in the third experimental group was not statistically different from the volunteer group (F=0.54, P=0.814), suggesting that the lumbar disc nucleus pulposus tissue of in vitro model samples fitted well with the volunteer group.

Conclusions

In this experiment, we successfully constructed an in vitro model of nucleus pulposus tissue proteoglycan that can be used for the quantitative evaluation of the MR-T1ρ imaging.

Changes in Infrapatellar Fat Pad Volume 6 to 12 Months After Anterior Cruciate Ligament Reconstruction and Associations With Patient-Reported Knee Function

CONTEXT

Hypertrophy of the infrapatellar fat pad (IFP) in idiopathic knee osteoarthritis has been linked to deleterious synovial changes and joint pain related to mechanical tissue impingement. Yet little is known regarding the IFP's volumetric changes after anterior cruciate ligament reconstruction (ACLR).

OBJECTIVES

To examine changes in IFP volume between 6 and 12 months after ACLR and determine associations between patient-reported outcomes and IFP volume at each time point as well as the volume change over time. In a subset of individuals, we examined interlimb IFP volume differences 12 months post-ACLR.

STUDY DESIGN

Prospective cohort study.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

We studied 26 participants (13 women, 13 men, age = 21.88 ± 3.58 years, body mass index = 23.82 ± 2.21 kg/m2) for our primary aims and 13 of those participants (8 women, 5 men, age = 21.15 ± 3.85 years, body mass index = 23.01 ± 2.01 kg/m2) for our exploratory aim.

MAIN OUTCOME MEASURE(S)

Using magnetic resonance imaging, we evaluated the IFP volume change between 6 and 12 months post-ACLR in the ACLR limb and between-limbs differences at 12 months in a subset of participants. International Knee Documentation Committee subjective knee evaluation (IKDC) scores were collected at 6-month and 12-month follow-ups, and associations between IFP volume and patient-reported outcomes were determined.

RESULTS

The IFP volume in the ACLR limb increased from 6 months (19.67 ± 6.30 cm3) to 12 months (21.26 ± 6.91 cm3) post-ACLR. Greater increases of IFP volume between 6 and 12 months were significantly associated with better 6-month IKDC scores (r = .44, P = .03). The IFP volume was greater in the uninjured limb (22.71 ± 7.87 cm3) than in the ACLR limb (20.75 ± 9.03 cm3) 12 months post-ACLR.

CONCLUSIONS

The IFP volume increased between 6 and 12 months post-ACLR; however, the IFP volume of the ACLR limb remained smaller than that of the uninjured limb at 12 months. In addition, those with better knee function 6 months post-ACLR demonstrated greater increases in IFP volume between 6 and 12 months post-ACLR. This suggests that greater IFP volumes may play a role in long-term joint health after ACLR.

The instrumented sheep knee to elucidate insights into osteoarthritis development and progression: A sensitive and reproducible platform for integrated research efforts

BACKGROUND

Osteoarthritis of the knee is a very common condition that has been difficult to treat. The majority of cases are considered idiopathic. Much research effort remains focused on biology rather than the biomechanics of such joints. Some new methods were developed and validated to better appreciate the subtleties of the biomechanical integrity of joints, and how changes in biomechanics can contribute to osteoarthritis.

METHODS

Over the past 15 years our lab has enhanced the sensitivity of the assessment of knee biomechanics of an instrumented, trained large animal model (sheep) of osteoarthritis and integrated the findings with biological and histological assessments. These new methods include gait analysis before and after injury followed by robotic validation post-sacrifice, and more recently using Fibre Bragg Grating sensors to detect alterations in cartilage stresses.

RESULTS

A review of the findings obtained with this model are presented. The findings indicate that sheep, like humans, exhibit individual characteristics. They also indicate that joint kinetics, rather than kinematics may better define the alterations induced by injury. With the addition of Fibre Bragg Grating sensors, it has been possible to measure with good accuracy, alterations to cartilage stresses following a controlled knee injury.

INTERPRETATION

Using this model as Proof of Concept, this sheep system can now be viewed as a sensitive platform to address many questions related to risk for development of idiopathic osteoarthritis of the human knee, the efficacy of potential interventions to correct biomechanical disruptions, and how joint biomechanics and biology are integrated during aging.

Association of Jump-Landing Biomechanics With Tibiofemoral Articular Cartilage Composition 12 Months After ACL Reconstruction

BACKGROUND

Excessively high joint loading during dynamic movements may negatively influence articular cartilage health and contribute to the development of posttraumatic osteoarthritis after anterior cruciate ligament reconstruction (ACLR). Little is known regarding the link between aberrant jump-landing biomechanics and articular cartilage health after ACLR.

PURPOSE/HYPOTHESIS

The purpose of this study was to determine the associations between jump-landing biomechanics and tibiofemoral articular cartilage composition measured using T1ρ magnetic resonance imaging (MRI) relaxation times 12 months postoperatively. We hypothesized that individuals who demonstrate alterations in jump-landing biomechanics, commonly observed after ACLR, would have longer T1ρ MRI relaxation times (longer T1ρ relaxation times associated with less proteoglycan density).

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

A total of 27 individuals with unilateral ACLR participated in this cross-sectional study. Jump-landing biomechanics (peak vertical ground-reaction force [vGRF], peak internal knee extension moment [KEM], peak internal knee adduction moment [KAM]) and T1ρ MRI were collected 12 months postoperatively. Mean T1ρ relaxation times for the entire weightbearing medial femoral condyle, lateral femoral condyle (global LFC), medial tibial condyle, and lateral tibial condyle (global LTC) were calculated bilaterally. Global regions of interest were further subsectioned into posterior, central, and anterior regions of interest. All T1ρ relaxation times in the ACLR limb were normalized to the uninjured contralateral limb. Linear regressions were used to determine associations between T1ρ relaxation times and biomechanics after accounting for meniscal/chondral injury.

RESULTS

Lower ACLR limb KEM was associated with longer T1ρ relaxation times for the global LTC (ΔR 2 = 0.24; P = .02), posterior LTC (ΔR 2 = 0.21; P = .03), and anterior LTC (ΔR 2 = 0.18; P = .04). Greater ACLR limb peak vGRF was associated with longer T1ρ relaxation times for the global LFC (ΔR 2 = 0.20; P = .02) and central LFC (ΔR 2 = 0.15; P = .05). Peak KAM was not associated with T1ρ outcomes.

CONCLUSION

At 12 months postoperatively, lower peak KEM and greater peak vGRF during jump landing were related to longer T1ρ relaxation times, suggesting worse articular cartilage composition.

Vibration improves gait biomechanics linked to posttraumatic knee osteoarthritis following anterior cruciate ligament injury

Anterior cruciate ligament reconstruction (ACLR) incurs a high risk of posttraumatic knee osteoarthritis (PTOA). Aberrant gait biomechanics contribute to PTOA and are attributable in part to quadriceps dysfunction. Vibration improves quadriceps function following ACLR, but its effects on gait biomechanics are unknown. The purpose of this study was to evaluate the effects of whole-body vibration (WBV) and local muscle vibration (LMV) on gait biomechanics in individuals with ACLR. Seventy-five volunteers (time since ACLR 27 ± 16 months) were randomized to WBV, LMV, or Control interventions. Walking biomechanics were assessed prior to and following a single exposure to the interventions. Outcomes included pre-post change scores in the ACLR limb for the peak vertical ground reaction force (vGRF) and its loading rate, peak internal knee extension (KEM) and abduction moments, and peak knee flexion and varus angles. LMV produced a significant decrease in the vGRF loading rate (-3.6 BW/s) that was greater than the changes in the WBV (-0.3 BW/s) and Control (0.5 BW/s) groups. Additionally, WBV produced an increase in the peak KEM (0.27% BW × Ht) that was greater than the change in the Control group (-0.17% BW × Ht) but not the LMV group (0.01% BW × Ht). Lower KEM and greater loading rates have been linked to declines in joint health following ACLR. WBV acutely increased the peak KEM and LMV decreased loading rates. These data suggest that vibration has the potential to mitigate aberrant gait biomechanics, and may represent an effective approach for reducing PTOA risk following ACLR.

Bridge-Enhanced Anterior Cruciate Ligament Repair Leads to Greater Limb Asymmetry and Less Cartilage Damage Than Untreated ACL Transection or ACL Reconstruction in the Porcine Model

BACKGROUND

The extent of posttraumatic osteoarthritis (PTOA) in the porcine anterior cruciate ligament (ACL) transection model is dependent on the surgical treatment selected. In a previous study, animals treated with bridge-enhanced ACL repair using a tissue-engineered implant developed less PTOA than those treated with ACL reconstruction (ACLR). Alterations in gait, including asymmetric weightbearing and shorter stance times, have been noted in clinical studies of subjects with osteoarthritis.

HYPOTHESIS

Animals receiving a surgical treatment that results in less PTOA (ie, bridge-enhanced ACL repair) would exhibit fewer longitudinal postoperative gait asymmetries over a 1-year period when compared with treatments that result in greater PTOA (ie, ACLR and ACL transection).

STUDY DESIGN

Controlled laboratory study.

METHODS

Thirty-six Yucatan minipigs underwent ACL transection and were randomized to receive (1) no further treatment, (2) ACLR, or (3) bridge-enhanced ACL repair. Gait analyses were performed preoperatively, and at 4, 12, 26, and 52 weeks postoperatively. Macroscopic cartilage assessments were performed at 52 weeks.

RESULTS

Knees treated with bridge-enhanced ACL repair had less macroscopic damage in the medial tibial plateau than those treated with ACLR or ACL transection (adjusted P = .03 for both comparisons). The knees treated with bridge-enhanced ACL repair had greater asymmetry in hindlimb maximum force and impulse loading at 52 weeks than the knees treated with ACL transection (adjusted P < .05 for both comparisons). Although not significant, there was a trend that knees treated with bridge-enhanced ACL repair had greater asymmetry in hindlimb maximum force and impulse loading (adjusted P < .10 for both comparisons) compared with ACLR.

CONCLUSION

Contrary to our hypothesis, the surgical treatment resulting in less macroscopic cartilage damage (ie, bridge-enhanced ACL repair) exhibited greater asymmetry in load-related gait parameters than the other surgical groups. This finding suggests that increased offloading of the surgical knee may be associated with a slower rate of PTOA development.

CLINICAL RELEVANCE

Less cartilage damage at 52 weeks was found in the surgical group that continued to protect the limb from full body weight during gait. This finding suggests that protection of the knee from maximum stresses may be important in minimizing the development of PTOA in the ACL-injured knee within 1 year.

Hamstrings Neuromuscular Function After Anterior Cruciate Ligament Reconstruction: A Systematic Review and Meta-Analysis

BACKGROUND

Hamstrings neuromuscular function is a crucial component of functional movement, and changes after anterior cruciate ligament (ACL) injury contribute to risk factors for secondary injury and long-term sequelae. To effectively treat muscular impairments, an accurate understanding of hamstrings neuromuscular function in patients with ACL reconstruction (ACLR) is needed.

OBJECTIVE

A systematic review and meta-analysis were undertaken to describe and quantify hamstrings neuromuscular function in individuals with ACLR compared to controls.

METHODS

We searched PubMed, Web of Science, SPORTDiscus, CINAHL, and EBSCOhost databases in October of 2020 for studies evaluating the difference between hamstrings electromyography (EMG) between individuals with ACLR and controls. Two independent reviewers assessed each paper for inclusion and quality. Means and standard deviations were extracted from each included study to allow random-effect size (ES) meta-analysis calculations for comparison of results.

RESULTS

Thirty-four studies were included for final review. From these, 5 categories of neuromuscular outcomes were identified, and studies were grouped accordingly: (1) muscle activation levels (EMG amplitude), (2) co-activation, (3) onset timing, (4) electromechanical delay, and (5) time-to-peak activity. Moderate to strong evidence indicates that individuals with ACLR demonstrate higher hamstrings EMG amplitude (normalized to % maximum voluntary isometric contraction) and hamstrings-to-quadriceps co-activation during gait and stair ambulation compared to controls. In addition, there was moderate evidence of longer electromechanical delay during knee flexion and greater hamstrings-to-quadriceps co-activation during knee extension compared to controls.

CONCLUSIONS

Greater hamstrings EMG amplitude and co-activation during gait and ambulation tasks and longer electromechanical delay of the hamstrings in individuals with ACLR align with clinical impairments following ACLR and have implications for re-injury risk and long-term joint health, thus warranting attention in rehabilitation.

Osteoarthritis year in review 2020: imaging

This narrative "Year in Review" highlights a selection of articles published between January 2019 and April 2020, to be presented at the OARSI World Congress 2020 within the field of osteoarthritis (OA) imaging. Articles were obtained from a PubMed search covering the above period, utilizing a variety of relevant search terms. We then selected original and review studies on OA-related imaging in humans, particularly those with direct clinical relevance, with a focus on the knee. Topics selected encompassed clinically relevant models of early OA, particularly imaging applications on cruciate ligament rupture, as these are of direct clinical interest and provide potential opportunity to evaluate preventive therapy. Further, imaging applications on structural modification of articular tissues in patients with established OA, by non-pharmacological, pharmacological and surgical interventions are summarized. Finally, novel deep learning approaches to imaging are reviewed, as these facilitate implementation and scaling of quantitative imaging application in clinical trials and clinical practice. Methodological or observational studies outside these key focus areas were not included. Studies focused on biology, biomechanics, biomarkers, genetics and epigenetics, and clinical studies that did not contain an imaging component are covered in other articles within the OARSI "Year in Review" series. In conclusion, exciting progress has been made in clinically validating human models of early OA, and the field of automated articular tissue segmentation. Most importantly though, it has been shown that structure modification of articular cartilage is possible, and future research should focus on the translation of these structural findings to clinical benefit.

Quadriceps Strength Symmetry Does Not Modify Gait Mechanics After Anterior Cruciate Ligament Reconstruction, Rehabilitation, and Return-to-Sport Training

BACKGROUND

After anterior cruciate ligament (ACL) reconstruction (ACLR), biomechanical asymmetries during gait are highly prevalent, persistent, and linked to posttraumatic knee osteoarthritis. Quadriceps strength is an important clinical measure associated with preoperative gait asymmetries and postoperative function and is a primary criterion for return-to-sport clearance. Evidence relating symmetry in quadriceps strength with gait biomechanics is limited to preoperative and early rehabilitation time points before return-to-sport training.

PURPOSE/HYPOTHESIS

The purpose was to determine the relationship between symmetry in isometric quadriceps strength and gait biomechanics after return-to-sport training in athletes after ACLR. We hypothesized that as quadriceps strength symmetry increases, athletes will demonstrate more symmetric knee joint biomechanics, including tibiofemoral joint loading during gait.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Of 79 athletes enrolled in the ACL-SPORTS Trial, 76 were participants in this study after completing postoperative rehabilitation and 10 return-to-sport training sessions (mean ± SD, 7.1 ± 2.0 months after ACLR). All participants completed biomechanical walking gait analysis and isometric quadriceps strength assessment using an electromechanical dynamometer. Quadriceps strength was calculated using a limb symmetry index (involved limb value / uninvolved limb value × 100). The biomechanical variables of interest included peak knee flexion angle, peak knee internal extension moment, sagittal plane knee excursion at weight acceptance and midstance, quadriceps muscle force at peak knee flexion angle, and peak medial compartment contact force. Spearman rank correlation (ρ) coefficients were used to determine the relationship between limb symmetry indexes in quadriceps strength and each biomechanical variable; alpha was set to .05.

RESULTS

Of the 76 participants, 27 (35%) demonstrated asymmetries in quadriceps strength, defined by quadriceps strength symmetry <90% (n = 23) or >110% (n = 4) (range, 56.9%-131.7%). For the biomechanical variables of interest, 67% demonstrated asymmetry in peak knee flexion angle; 68% and 83% in knee excursion during weight acceptance and midstance, respectively; 74% in internal peak knee extension moment; 57% in medial compartment contact force; and 74% in quadriceps muscle force. There were no significant correlations between quadriceps strength index and limb symmetry indexes for any biomechanical variable after return-to-sport training (P > .129).

CONCLUSION

Among those who completed return-to-sport training after ACLR, subsequent quadriceps strength symmetry was not correlated with the persistent asymmetries in gait biomechanics. After a threshold of quadriceps strength is reached, restoring strength alone may not ameliorate gait asymmetries, and current clinical interventions and return-to-sport training may not adequately target gait.

Lower Limb Muscle Size after Anterior Cruciate Ligament Injury: A Systematic Review and Meta-Analysis

BACKGROUND

Anterior cruciate ligament (ACL) injury is known to have a number of deleterious effects on lower limb muscle function. Alterations in muscle size are one such effect that have implications towards reductions in strength and functioning of the lower limbs. However, a comprehensive analysis of alterations in muscle size has yet to be undertaken.

OBJECTIVE

To systematically review the evidence investigating lower limb muscle size in ACL injured limbs.

DESIGN

Systematic review DATA SOURCES: Database searches of Medline, SPORTDiscus, Embase, Cinahl and Web of Science as well as citation tracking and manual reference list searching.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Individuals with ACL deficient or reconstructed limbs with an assessment of lower limb muscle size and control limb data (contralateral or uninjured control group) METHODS: Risk of bias assessment was completed on included studies. Data were extracted and where possible meta-analyses performed. Best evidence synthesis was also undertaken.

RESULTS

49 articles were included in this review, with 37 articles included in the meta-analyses. 66 separate meta-analyses were performed using various measures of lower limb muscle size. Across all measures, ACL deficient limbs showed lesser quadriceps femoris muscle size (d range = - 0.35 to - 0.40), whereas ACL reconstructed limbs showed lesser muscle size in the quadriceps femoris (d range = - 0.41 to - 0.69), vastus medialis (d = - 0.25), vastus lateralis (d = - 0.31), hamstrings (d = - 0.28), semitendinosus (d range = - 1.02 to - 1.14) and gracilis (d range = - 0.78 to - 0.99) when compared to uninjured limbs.

CONCLUSION

This review highlights the effect ACL injury has on lower limb muscle size. Regardless of whether an individual chooses a conservative or surgical approach, the quadriceps of the injured limb appear to have lesser muscle size compared to an uninjured limb. When undertaking reconstructive surgery with a semitendinosus/gracilis tendon graft, the harvested muscle shows lesser muscle size compared to the uninjured limb.

Gait Biomechanics in Individuals Meeting Sufficient Quadriceps Strength Cutoffs Following Anterior Cruciate Ligament Reconstruction

CONTEXT

Quadriceps weakness is associated with disability and aberrant gait biomechanics following anterior cruciate ligament reconstruction (ACLR). Strength sufficiency cutoff scores, that normalize quadriceps strength to the mass of an individual, are capable of predicting individuals who will report better function following ACLR. Yet, it remains unknown if gait biomechanics differ between individuals who meet a strength sufficiency cutoff (strong) compared to those who do not (weak).

OBJECTIVE

Determine if vertical ground reaction force (vGRF), knee flexion angle (KFA) and internal knee extension moment (KEM) differ between strong and weak individuals with an ACLR throughout stance phase of walking.

DESIGN

Comparison-control.

SETTING

Laboratory Participants: Individuals who received unilateral ACLR ≥12 months prior to testing were dichotomized into strong (n=31) and weak groups (n=116).

MAIN OUTCOME MEASURES

Maximal isometric quadriceps strength was collected at 90° of knee flexion using an isokinetic dynamometer and normalized to body mass. Individuals demonstrating ≥3.0Nm/kg were considered strong. Three-dimensional gait biomechanics were collected at a self-selected walking speed. Biomechanical data were time-normalized to 100% of stance phase. vGRF were normalized to body weight (BW), and KEM was normalized to BW*height. Pairwise comparison functions were calculated for each outcome to identify between-group differences for each percentile of stance.

RESULTS

vGRF was significantly greater in weak participants for the first 22% of stance (average difference of 6.2% BW) and lesser in weak participants between 36-43% of stance (1.4% BW). KFA was significantly greater (i.e., more flexion) in strong participants between 6-62% of stance (2.3°) and lesser (i.e., less flexion) between 68-79% of stance (1.0°). KEM was significantly greater in strong participants between 7-62% of stance (0.007 BW*height).

CONCLUSIONS

ACLR individuals able to generate knee extension torque ≥3.0Nm/kg exhibit different biomechanical gait profiles compared to weak individuals, which may allow for better energy attenuation following ACLR.

In vivo Compositional Changes in the Articular Cartilage of the Patellofemoral Joint following Anterior Cruciate Ligament Reconstruction

OBJECTIVE

To compare T1ρ relaxation times of the medial and lateral regions of the patella and femoral trochlea at 6 and 12 months post-anterior cruciate ligament reconstruction (ACLR) on the ACLR and contralateral limb. Greater T1ρ relaxation times are associated with a lesser proteoglycan density of articular cartilage.

METHODS

Twenty individuals (11 males, 9 females; age=22±3.9yrs; mass=76.11±13.48kg; height=178.32±12.32) who underwent a previous unilateral ACLR using a patellar tendon autograft. Magnetic resonance images from both limbs were acquired at 6 and 12 months post-ACLR. Voxel by voxel T1ρ relaxation times were calculated using a five-image sequence. The medial and lateral regions of the femoral trochlea and patellar articular cartilage were manually segmented on both limbs. Separate limb (ACLR and contralateral limb) by time (6-months and 12-months) ANOVAs were performed for each region (P<0.05).

RESULTS

For the medial patella and lateral trochlea, T1ρ relaxation times increased in both limbs between 6 and 12-months post-ACLR (medial patella: P=0.012; lateral trochlea: P=0.043). For the lateral patella, T1ρ relaxation times were significantly greater on the contralateral limb compared to the ACLR limb (P=0.001). The T1ρ relaxation times of the medial trochlea on the ACLR limb were significantly greater at 6 (P=0.005) and 12-months (P<0.001) compared to the contralateral limb. T1ρ relaxation times of the medial trochlea significantly increased from 6 to 12-months on the ACLR limb (P=0.003).

CONCLUSION

Changes in T1ρ relaxation times occur within the first 12 months following ACLR in specific regions of the patellofemoral joint on the ACLR and contralateral limb.

Factors Affecting the Femoral Cartilage Thickness After Anterior Cruciate Ligament Reconstruction

BACKGROUND

This study aimed to evaluate the changes in the distal femoral cartilage thickness in patients that underwent anterior cruciate ligament reconstruction (ACLR) and to analyze their association with concomitant meniscal surgery, knee muscle strength, kinesophobia, and physical activity level.

METHODS

The demographic characteristics and surgical data of 47 male patients that underwent unilateral ACLR (mean, 27.55 ± 5.63; range, 18-40 years) were evaluated. The patients were assessed in three groups depending on surgery: isolated ACLR (n = 15), ACLR + partial medial meniscus resection (ACLR&M) (n = 16), and ACLR + medial meniscus repair (ACLR&MR) (n = 16). The medial (MCCT), intercondylar (ICCT), and lateral (LCCT) femoral cartilage thicknesses on both limbs were measured using ultrasonography. The extensor and flexor muscles strength of the knees was assessed using an isokinetic dynamometer at 60°/s. The physical activity level was evaluated by the International Physical Activity Questionnaire (IPAQ) short form and Tegner Activity Scale (TAS). The fear of movement was assessed by the Tampa Scale for Kinesiophobia Questionnaire (TSKQ).

RESULTS

The postoperative mean follow-up duration was 32.24 ± 9.17 months. MCCT and LCCT were significantly decreased in the ACLR&M group (p < 0.001 and p = 0.019, respectively). MCCT, ICCT and LCCT were significantly decreased in the ACLR&MR group (p = 0.017, p = 0.011, and p = 0.004, respectively). No significant change was found in the ACLR group. Cartilage thickness changes were not significantly correlated with the knee muscle strength, IPAQ, TAS and TSKQ scores in all groups (p > 0.05).

CONCLUSION

The results showed partial meniscectomy and meniscus repair at the time of ACLR as important risk factors for decreased chondral thickness.

Michigan Initiative for Anterior Cruciate Ligament Rehabilitation (MiACLR): A Protocol for a Randomized Clinical Trial

OBJECTIVE

Restoring quadriceps muscle strength following anterior cruciate ligament reconstruction (ACLR) may prevent the posttraumatic osteoarthritis that affects over 50% of knees with ACLR. However, a fundamental gap exists in our understanding of how to maximize muscle strength through rehabilitation. Neurological deficits and muscle atrophy are 2 of the leading mechanisms of muscle weakness after ACLR. High-intensity neuromuscular electrical stimulation (NMES) and eccentric exercise (ECC) have been shown to independently target these mechanisms. If delivered in succession, NMES and then ECC may be able to significantly improve strength recovery. The objectives of this study were to evaluate the ability of NMES combined with ECC to restore quadriceps strength and biomechanical symmetry and maintain cartilage health at 9 and 18 months after ACLR.

METHODS

This study is a randomized, double-blind, placebo-controlled, single-center clinical trial conducted at the University of Michigan. A total of 112 participants between the ages of 14 and 45 years and with an anterior cruciate ligament rupture will be included. Participants will be randomly assigned 1:1 to NMES combined with ECC or NMES placebo combined with ECC placebo. NMES or NMES placebo will be delivered 2 times per week for 8 weeks beginning 10 to 14 days postoperatively and will be directly followed by 8 weeks of ECC or ECC placebo delivered 2 times per week. The co-primary endpoints are change from baseline to 9 months and change from baseline to 18 months after ACLR in isokinetic quadriceps strength symmetry. Secondary outcome measures include isometric quadriceps strength, quadriceps activation, quadriceps muscle morphology (cross-sectional area), knee biomechanics (sagittal plane knee angles and moments), indexes of patient-reported function, and cartilage health (T1ρ and T2 relaxation time mapping on magnetic resonance imaging).

IMPACT

The findings from this study might identify an intervention capable of targeting the lingering quadriceps weakness after ACLR and in turn prevent deterioration in cartilage health after ACLR, thereby potentially improving function in this patient population.

Examination of Corticospinal and Spinal Reflexive Excitability During the Course of Postoperative Rehabilitation After Anterior Cruciate Ligament Reconstruction

OBJECTIVE

To investigate corticospinal and spinal reflexive excitability and quadriceps strength in healthy athletes and athletes after anterior cruciate ligament reconstruction (ACLR) over the course of rehabilitation.

DESIGN

Prospective cohort study.

METHODS

Eighteen athletes with ACLR and 18 healthy athletes, matched by sex, age, and activity, were tested at (1) 2 weeks after surgery, (2) the "quiet knee" time point, defined as full range of motion and minimal effusion, and (3) return to running, defined as achieving a quadriceps index of 80% or greater. We measured (1) corticospinal excitability, using resting motor threshold (RMT) and motor-evoked potential amplitude at a stimulator intensity of 120% of RMT (MEP₁₂₀) to the vastus medialis, (2) spinal reflexive excitability, calculating the ratio of the maximal Hoffmann reflex to the maximal M-wave to the vastus medialis, and (3) isometric quadriceps strength.

RESULTS

The ACLR group had higher RMTs in the nonsurgical limb and higher MEP₁₂₀ in the surgical limb at all time points. The healthy-athlete group did not have interlimb differences. The RMT was positively associated with quadriceps strength 2 weeks after surgery; MEP₁₂₀ was associated with quadriceps strength at all time points.

CONCLUSION

Compared to healthy athletes, athletes after ACLR had altered corticospinal excitability that did not change from 2 weeks after surgery to the time of return to running. J Orthop Sports Phys Ther 2020;50(9):516-522. Epub 1 Aug 2020. doi:10.2519/jospt.2020.9329.

The Use of Recombinant Human Growth Hormone to Protect Against Muscle Weakness in Patients Undergoing Anterior Cruciate Ligament Reconstruction: A Pilot, Randomized Placebo-Controlled Trial

BACKGROUND

Anterior cruciate ligament (ACL) tears are common knee injuries. Despite undergoing extensive rehabilitation after ACL reconstruction (ACLR), many patients have persistent quadriceps muscle weakness that limits their successful return to play and are also at an increased risk of developing knee osteoarthritis (OA). Human growth hormone (HGH) has been shown to prevent muscle atrophy and weakness in various models of disuse and disease but has not been evaluated in patients undergoing ACLR.

HYPOTHESIS

Compared with placebo treatment, a 6-week perioperative treatment course of HGH would protect against muscle atrophy and weakness in patients undergoing ACLR.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 2.

METHODS

A total of 19 male patients (aged 18-35 years) scheduled to undergo ACLR were randomly assigned to the placebo (n = 9) or HGH (n = 10) group. Patients began placebo or HGH treatment twice daily 1 week before surgery and continued through 5 weeks after surgery. Knee muscle strength and volume, patient-reported outcome scores, and circulating biomarkers were measured at several time points through 6 months after surgery. Mixed-effects models were used to evaluate differences between treatment groups and time points, and as this was a pilot study, significance was set at P < .10. The Cohen d was calculated to determine the effect size.

RESULTS

HGH was well-tolerated, and no differences in adverse events between the groups were observed. The HGH group had a 2.1-fold increase in circulating insulin-like growth factor 1 over the course of the treatment period (P < .05; d = 2.93). The primary outcome measure was knee extension strength, and HGH treatment increased normalized peak isokinetic knee extension torque by 29% compared with the placebo group (P = .05; d = 0.80). Matrix metalloproteinase-3 (MMP3), which was used as an indirect biomarker of cartilage degradation, was 36% lower in the HGH group (P = .05; d = -1.34). HGH did not appear to be associated with changes in muscle volume or patient-reported outcome scores.

CONCLUSION

HGH improved quadriceps strength and reduced MMP3 levels in patients undergoing ACLR. On the basis of this pilot study, further trials to more comprehensively evaluate the ability of HGH to improve muscle function and potentially protect against OA in patients undergoing ACLR are warranted.

REGISTRATION

NCT02420353 ( ClinicalTrials.gov identifier).

Osteoarthritis year in review 2019: mechanics

Mechanics play a critical - but not sole - role in the pathogenesis of osteoarthritis, and recent research has highlighted how mechanical constructs are relevant at the cellular, joint, and whole-body level related to osteoarthritis outcomes. This review examined papers from April 2018 to April 2019 that reported on the role of mechanics in osteoarthritis etiology, with a particular emphasis on studies that focused on the interaction between movement and tissue biomechanics with other clinical outcomes relevant to the pathophysiology of osteoarthritis. Studies were grouped by themes that were particularly prevalent from the past year. Results of the search highlighted the large exposure of knee-related research relative to other body areas, as well as studies utilizing laboratory-based motion capture technology. New research from this past year highlighted the important role that rate of exerted loads and rate of muscle force development - rather than simply force capacity (strength) - have in OA etiology and treatment. Further, the role of muscle activation patterns in functional and structural aspects of joint health has received much interest, though findings remain equivocal. Finally, new research has identified potential mechanical outcome measures that may be related to osteoarthritis disease progression. Future research should continue to combine knowledge of mechanics with other relevant research techniques, and to identify mechanical markers of joint health and structural and functional disease progression that are needed to best inform disease prevention, monitoring, and treatment.