Whole-body kinematics of squats two decades following anterior cruciate ligament injury

BACKGROUND

Kinematic studies suggest that injury of the anterior cruciate ligament (ACL) leads to long-lasting movement deficits or compensations to unload the injured knee. This study evaluated lower body kinematics during squats in individuals who suffered unilateral ACL-injury more than 20 years ago.

METHOD

Using motion capture, we compared maximum squat depth, time to complete the squat task, detailed kinematics, estimated kinetic-chain joint moments 0- 80° knee flexion, and weight distribution between legs across three groups with (ACLR, n = 27) and without ACL-reconstructive surgery (ACLPT, physiotherapy only, n = 28), and age-matched non-injured asymptomatic Controls (n = 31, average age across groups 47 years).

RESULTS

ACLPT demonstrated significantly reduced squat depth compared to Controls (p = 0.004), whereas ACLR performed similarly to Controls (p = 1.000). Other outcome variables were comparable between groups. All participants nevertheless demonstrated asymmetric weight distribution between legs but without systematic unloading of the injured side in the ACLgroups.

CONCLUSION

Expected compensatory strategies were not found in the ACL-groups, while poorer squat performance in the ACL-deficient group may depend on pure knee-joint mechanics, or lifestyle factors attributed to a less stable knee decades after ACL-injury.

The Muscle Strength of the Knee Joint after ACL Reconstruction Depends on the Number and Frequency of Supervised Physiotherapy Visits

The aim of this study in anterior cruciate ligament reconstruction (ACLR) patients was to assess the effect of six months of supervised physiotherapy with a higher number of visits (SPHNV) compared to supervised physiotherapy with a lower number of visits (SPLNV) on the maximal peak torque (PT) and isometric torque (IT) of values obtained for hamstring (H) and quadriceps (Q) muscles of the knee joints under isokinetic and isometric conditions. Hypothesis: SPHNV improves IT and PT more than SPLNV. Group I had ACLR with a higher number of visits (n = 20), Group II had ACLR with a lower number of visits (n = 20), and Group III served as the control (n = 20). In Groups I and II, IT values were measured for quadriceps and hamstring muscles of the knee joints in the 13th and 24th weeks and for PT in the 18th and 24th weeks after ACLR (60 and 180 °/s). In group III, the measurements were taken once. The isometric torque and isokinetic peak torque values were measured in N*m and they were normalized to body mass as relative IT (RIT) and relative PT (RPT) were expressed in N*m/kg. Results: In both ACLR groups, the RIT and RPT values obtained from the operated knee joints significantly increased in the 24 weeks following ACLR compared to the uninvolved side. Group II had significantly lower RIT and RPT values for quadriceps and hamstring muscles of the operated limbs compared with the uninvolved limbs (p = 0.008, p = 0.001). In group I, the larger number of visits positively correlated with the higher PT for quadriceps and hamstring muscles of the operated and uninvolved knees (from r = 0.506; p = 0.023 too r = 0.566; p = 0.009), respectively. Six months of SPHNV positively correlated with and improved the IT and PT values in patients after ACLR much more significantly than six months of SPLNV.

Blood Flow Restriction Training Can Improve Peak Torque Strength in Chronic Atrophic Postoperative Quadriceps and Hamstrings Muscles

PURPOSE

To report a prospective study of patients who underwent blood flow restriction training (BFRT) for marked quadriceps or hamstring muscle deficits after failure to respond to traditional rehabilitation after knee surgery.

METHODS

The BFRT protocol consisted of 4 low resistance exercises (30% of 1 repetition maximum): leg press, knee extension, mini-squats, and hamstring curls with 60% to 80% limb arterial occlusion pressure. Knee peak isometric muscle torque (60° flexion) was measured on an isokinetic dynamometer.

RESULTS

Twenty-seven patients (18 females, 9 males; mean age, 40.1 years) with severe quadriceps and/or hamstrings deficits were enrolled from April 2017 to January 2020. They had undergone a mean of 5.3 ± 3.5 months of outpatient therapy and 22 ± 10 supervised therapy visits and did not respond to traditional rehabilitation. Prior surgery included anterior cruciate ligament reconstruction, partial or total knee replacements, meniscus repairs, and others. All patients completed 9 BFRT sessions, and 14 patients completed 18 sessions. The mean quadriceps and hamstrings torque deficits before BFRT were 43% ± 16% and 38% ± 14%, respectively. After 9 BFRT sessions, statistically significant improvements were found in muscle peak torque deficits for the quadriceps (P = .003) and hamstring (P = .02), with continued improvements after 18 sessions (P = .004 and P = .002, respectively). After 18 BFRT sessions, the peak quadriceps and hamstring peak torques increased > 20% in 86% and 76% of the patients, respectively. The failure rate of achieving this improvement in peak quadriceps and hamstring torque after 18 BFRT sessions was 14% and 24%, respectively.

CONCLUSIONS

BFRT produced statistically significant improvements in peak quadriceps and hamstring torque measurements after 9 and 18 sessions in a majority of patients with severe quadriceps and hamstring strength deficits that had failed to respond to many months of standard and monitored postoperative rehabilitation.

LEVEL OF EVIDENCE

Level IV therapeutic case series.

Improvements in asymmetry in knee flexion motion during landing are associated with the postoperative period and quadriceps strength after anterior cruciate ligament reconstruction

This study investigated the relationship between quadriceps strength and knee kinematics during a drop vertical jump (DVJ) at 6, 9 and 12 months after anterior cruciate ligament reconstruction (ACLR) in 9 male and 22 female athletes (16.6 ± 2.1 years old). Isokinetic quadriceps strength was measured by a dynamometer (Biodex System 3). Knee flexion excursion was assessed using two-dimensional analysis. Knee flexion excursion at 6 months was significantly smaller in the involved limb than in the uninvolved limb independent of quadriceps strength (56.7° ± 9.3°, 63.4° ± 11.4°, P < 0.001). At 9 months, only the low quadriceps strength group demonstrated a similar interlimb difference (57.2°± 12.3°, 63.3° ± 10.5°, P < 0.001). At 12 months, there was no significant interlimb difference in knee flexion excursion regardless of quadriceps strength. These findings indicate that restoration in symmetrical knee flexion excursion during a DVJ requires rehabilitation as well as quadriceps strength.

Neuromuscular Function of the Knee Joint Following Knee Injuries: Does It Ever Get Back to Normal? A Systematic Review with Meta-Analyses

BACKGROUND

Neuromuscular deficits are common following knee injuries and may contribute to early-onset post-traumatic osteoarthritis, likely mediated through quadriceps dysfunction.

OBJECTIVE

To identify how peri-articular neuromuscular function changes over time after knee injury and surgery.

DESIGN

Systematic review with meta-analyses.

DATA SOURCES

PubMed, Web of Science, Embase, Scopus, CENTRAL (Trials).

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Moderate and high-quality studies comparing neuromuscular function of muscles crossing the knee joint between a knee-injured population (ligamentous, meniscal, osteochondral lesions) and healthy controls. Outcomes included normalized isokinetic strength, muscle size, voluntary activation, cortical and spinal-reflex excitability, and other torque related outcomes.

RESULTS

A total of 46 studies of anterior cruciate ligament (ACL) and five of meniscal injury were included. For ACL injury, strength and voluntary activation deficits were evident (moderate to strong evidence). Cortical excitability was not affected at < 6 months (moderate evidence) but decreased at 24+ months (moderate evidence). Spinal-reflex excitability did not change at < 6 months (moderate evidence) but increased at 24+ months (strong evidence). We also found deficits in torque variability, rate of torque development, and electromechanical delay (very limited to moderate evidence). For meniscus injury, strength deficits were evident only in the short-term. No studies reported gastrocnemius, soleus or popliteus muscle outcomes for either injury. No studies were found for other ligamentous or chondral injuries.

CONCLUSIONS

Neuromuscular deficits persist for years post-injury/surgery, though the majority of evidence is from ACL injured populations. Muscle strength deficits are accompanied by neural alterations and changes in control and timing of muscle force, but more studies are needed to fill the evidence gaps we have identified. Better characterisation and therapeutic strategies addressing these deficits could improve rehabilitation outcomes, and potentially prevent PTOA.

TRIAL REGISTRATION NUMBER

PROSPERO CRD42019141850.

Effect of Graft Type on Thigh Circumference, Knee Range of Motion, and Lower-Extremity Strength in Pediatric and Adolescent Males Following Anterior Cruciate Ligament Reconstruction

CONTEXT

To treat anterior cruciate ligament (ACL) injury, ACL reconstruction (ACLR) surgery is currently a standard of the care. However, effect of graft type including bone-patellar tendon-bone (BTB), hamstring tendon, or iliotibial band (ITB) on thigh size, knee range of motion (ROM), and muscle strength are understudied.

OBJECTIVE

To compare postoperative thigh circumference, knee ROM, and hip and thigh muscle strength in adolescent males who underwent ACLR, based on the 3 different autograft types: BTB, hamstring (HS), and ITB.

SETTING

Biomechanical laboratory.

PARTICIPANTS

Male ACLR patients who are younger than 22 years of age (total N = 164).

INTERVENTION

At 6- to 9-month postoperative visits, thigh circumference, knee ROM, and hip and thigh muscle strength were measured.

MAIN OUTCOME MEASURES

Deficits of each variable between the uninvolved and ACLR limb were compared for pediatric and adolescent ACLR males in the BTB, HS, and ITB cohorts. Baseline characteristics, including physical demographics and meniscus tear status, were compared, and differences identified were treated as covariates and incorporated in analysis of covariance.

RESULTS

Data were from 164 adolescent male ACLR patients [mean age 15.7 (1.2) years]. There were no statistical differences in thigh circumference, knee ROM, hip abductor, and hip-extensor strength among the 3 autografts. However, patients with BTB demonstrated 12.2% deficits in quadriceps strength compared with 0.5% surplus in HS patients (P = .002) and 1.2% deficits in ITB patients (P = .03). Patients with HS showed 31.7% deficits in hamstring strength compared with 5.4% deficits in BTB (P = .001) and 7.7% deficits in ITB (P = .001) groups at 6- to 9-month postoperative visits.

CONCLUSION

Adolescent male ACLR patients with BTB and HS autografts demonstrated significant deficits in quadriceps and hamstring strength, respectively, at 6 to 9 months postoperatively. Minimal lower-extremity strength deficits were demonstrated in pediatric male ACLR patients undergoing ITB harvest.

Is Pre-operative Quadriceps Strength a Predictive Factor for the Outcomes of Anterior Cruciate Ligament Reconstructions

Persistent quadriceps weakness prevents patients from returning to sports after ACL reconstruction. Pre-operative quadriceps strength was indicated as an important factor for the outcomes of ACL reconstruction. However, the existing evidence is controversial. Therefore, this systematic review was conducted to summarize and evaluate the relationship between pre-operative quadriceps strength and the outcomes following ACL reconstruction, and to summarize the predictive value of pre-operative quadriceps strength for satisfactory post-operative outcomes. Pubmed, WOS, Embase, CINAHL and SportDiscus were searched to identify eligible studies according to PRISMA guidelines. Relevant data was extracted regarding quadriceps strength assessment methods, pre-operative quadriceps strength, participants treatment protocols, post-operative outcomes, follow-up time points and the relevant results of each individual study. Twelve cohort studies (Coleman methodology score: 62±10.4; from 44-78) with 1773 participants included. Follow-up period ranged from 3 months to 2 years. Moderate evidence supports the positive association between pre-operative quadriceps strength and post-operative quadriceps strength; weak evidence supports the positive association between pre-operative quadriceps strength and post-operative functional outcomes. By now, there is no consensus on the predictive value of pre-operative quadriceps strength for achieving satisfactory quadriceps strength after ACLR. To conclude, pre-operative quadriceps strength should be taken into consideration when predict patient recovery of ACLR.

Elevating the Noninvolved Limb Reduces Knee Extensor Asymmetry During Squat Exercise in Persons With Reconstructed Anterior Cruciate Ligament

Jean, LMY and Chiu, LZF. Elevating the noninvolved limb reduces knee extensor asymmetry during squat exercise in persons with reconstructed anterior cruciate ligament. J Strength Cond Res 34(8): 2120-2127, 2020-Anterior cruciate ligament (ACL)-injured individuals use less knee extensor net joint moment (NJM) in the involved vs. noninvolved limb during squat exercises. The objective of this research was to examine if knee extensor NJM symmetry between the involved and noninvolved limbs could be attained with a modified squat. Six individuals with unilateral ACL reconstructed knees performed bilateral squats under normal conditions and with their noninvolved limb elevated on a 5-cm platform. Knee extensor NJM was determined using 3-dimensional motion analysis. Knee extensor NJM was lower in the involved compared with the noninvolved limb (95% confidence interval [CI], 0.08-0.28 N·m·kg; d = 1.66 SD) during normal squats. Knee extensor NJM was greater in the involved (95% CI, 0.02-0.18 N·m·kg; d = 0.57 SD) and lower in the noninvolved (95% CI, -0.25 to -0.07 N·m·kg; d = 1.85 SD) limbs in the elevated vs. normal squats. Knee extensor NJM was not different between limbs when the noninvolved limb was elevated (95% CI, -0.26 to 0.11 N·m·kg; d = 0.48 SD). Persons with ACL reconstruction exhibit knee extensor asymmetry during bilateral squats. Elevating the noninvolved limb reduces knee extensor NJM asymmetry between the involved and noninvolved limbs during squat exercise.

Two-Plane Assessment of Knee Muscles Isometric and Isokinetic Torques After Anterior Cruciate Ligament Reconstruction

Background

We tested the hypothesis that, in patients participating in 17 weeks of postoperative physiotherapy after anterior cruciate ligament reconstruction (ACLR), maximal isometric torque (IT) and peak torque (PT) generated by the muscles affecting the operated knee joint in the sagittal and transverse planes are not restored. We also present the application of IT and PT measurements of the muscles affecting the knee joint in 2 planes of motion.

Material/Methods

IT and PT of the knee extensor and flexor muscles and the muscles internally rotating the shin were measured in 30 males who participated in postoperative physiotherapy for 17 weeks after ACLR (ACLR group) and 30 males with no injuries (control group).

Results

Significantly lower IT and PT values were noted in the operated knee extensors and flexors. The differences were also noted in the PT for the muscles internally rotating the shin and in the IT of those muscles in the position of 25° of internal rotation. Significantly lower relative IT and PT values were noted for studied muscle groups in comparison to the control group.

Conclusions

Seventeen weeks of postoperative physiotherapy after ACLR did not result in complete restoration of IT and PT of the muscles affecting the operated knee joint, suggesting that even after 17 weeks of physiotherapy following ACLR, athletes may not be ready to return to sports. The results demonstrate the usefulness of biplanar analysis of muscle strength under isometric and isokinetic conditions in the monitoring and assessment of physiotherapeutic procedures.

Contribution of Neuromuscular Factors to Quadriceps Asymmetry After Anterior Cruciate Ligament Reconstruction

CONTEXT

  To quantify quadriceps weakness after anterior cruciate ligament reconstruction (ACLR), researchers have often analyzed only peak torque. However, analyzing other characteristics of the waveform, such as the rate of torque development (RTD), time to peak torque (TTP), and central activation ratio (CAR), can lend insight into the underlying neuromuscular factors that regulate torque development.

OBJECTIVE

  To determine if interlimb neuromuscular asymmetry was present in patients with ACLR at the time of clearance to return to activity.

DESIGN

  Cross-sectional study.

SETTING

  Laboratory.

PATIENTS OR OTHER PARTICIPANTS

  A total of 10 individuals serving as controls (6 men, 4 women; age = 23.50 ± 3.44 years, height = 1.73 ± 0.09 m, mass = 71.79 ± 9.91 kg) and 67 patients with ACLR (43 men, 24 women; age = 21.34 ± 5.73 years, height = 1.74 ± 0.11 m, mass = 77.85 ± 16.03 kg, time postsurgery = 7.52 ± 1.36 months) participated.

MAIN OUTCOME MEASURE(S)

  Isokinetic (60°/s) and isometric quadriceps strength were measured. Peak torque, TTP, and RTD were calculated across isometric and isokinetic trials, and CAR was calculated from the isometric trials via the superimposed burst. Repeated-measures analyses of variance were used to compare limbs in the ACLR and control groups.

RESULTS

  No between-limbs differences were detected in the control group ( P > .05). In the ACLR group, the involved limb demonstrated a longer TTP for isokinetic strength ( P = .04; Cohen d effect size [ES] = 0.18; 95% confidence interval [CI] = -0.16, 0.52), lower RTD for isometric ( P < .001; Cohen d ES = 0.73; 95% CI = 0.38, 1.08) and isokinetic ( P < .001; Cohen d ES = 0.84; 95% CI = 0.49, 1.19) strength, lower CAR ( P < .001; Cohen d ES = 0.37; 95% CI = 0.03, 0.71), and lower peak torque for isometric ( P < .001; Cohen d ES = 1.28; 95% CI = 0.91, 1.65) and isokinetic ( P < .001; Cohen d ES = 1.15; 95% CI = 0.78, 1.52) strength.

CONCLUSIONS

  Interlimb asymmetries at return to activity after ACLR appeared to be regulated by several underlying neuromuscular factors. We theorize that interlimb asymmetries in isometric and isokinetic quadriceps strength were associated with changes in muscle architecture. Reduced CAR, TTP, and RTD were also present, indicating a loss of motor-unit recruitment or decrease in firing rate.

Isokinetic Extension Strength Is Associated With Single-Leg Vertical Jump Height

Background

Isokinetic strength testing is an important tool in the evaluation of the physical capacities of athletes as well as for decision making regarding return to sports after anterior cruciate ligament (ACL) reconstruction in both athletes and the lay population. However, isokinetic testing is time consuming and requires special testing equipment.

Hypothesis

A single-jump test, regardless of leg dominance, may provide information regarding knee extension strength through the use of correlation analysis of jump height and peak torque of isokinetic muscle strength.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

A total of 169 patients who underwent ACL reconstruction were included in this study. Isokinetic testing was performed on the injured and noninjured legs. Additionally, a single-leg countermovement jump was performed to assess jump height using a jump accelerometer sensor. Extension strength values were used to assess the association between isokinetic muscle strength and jump height.

Results

The sample consisted of 60 female (mean age, 20.8 ± 8.3 years; mean weight, 61.7 ± 6.5 kg; mean height, 167.7 ± 5.3 cm) and 109 male (mean age, 23.2 ± 7.7 years; mean weight, 74.6 ± 10.2 kg; mean height, 179.9 ± 6.9 cm) patients. Bivariate correlation analysis showed an association (r = 0.56, P < .001) between jump height and isokinetic extension strength on the noninvolved side as well as an association (r = 0.52, P < .001) for the involved side. Regression analysis showed that in addition to jump height (beta = 0.49, P < .001), sex (beta = -0.17, P = .008) and body mass index (beta = 0.37, P < .001) affected isokinetic strength. The final model explained 51.1% of the variance in isokinetic muscle strength, with jump height having the strongest impact (beta = 0.49, P < .001) and explaining 31.5% of the variance.

Conclusion

Initial analysis showed a strong association between isokinetic strength and jump height. The study population encompassed various backgrounds, skill levels, and activity profiles, which might have affected the outcome. Even after controlling for age and sex, isokinetic strength was still moderately associated with jump height. Therefore, the jump technique and type of sport should be considered in future research.

Relationships Between Knee Extension Moments During Weighted and Unweighted Gait and Strength Measures That Predict Knee Moments After ACL Reconstruction

Background:

Weighted gait increases internal knee extension moment impulses (KEMI) in the anterior cruciate ligament–reconstructed (ACLR) limb; however, limb differences persist.

Hypotheses:

(1) KEMI during normal gait will influence KEMI during weighted gait and (2) peak knee extension (PKE) torque and time to reach PKE torque will predict KEMI during gait tasks.

Study Design:

Descriptive laboratory study.

Methods:

Twenty-four women and 14 men completed 3 gait tasks (unweighted, vest, sled) and strength testing after discharge from rehabilitation and clearance to return to sports. KEMI were calculated during the first 25% of stance. PKE torque and time to reach PKE torque were obtained using a dynamometer. Data on the ACLR limb and symmetry indices (SIs) were analyzed for each sex.

Results:

Women presented with asymmetrical PKE torques and KEMI across tasks. There were three correlations noted for KEMI: between the walk and vest, walk and sled, and vest and sled tasks. Slower time to PKE torque predicted limb asymmetries across tasks and KEMI in the ACLR limb during the sled task. Men presented with asymmetrical PKE torques and KEMI during the sled task. There was a correlation noted for KEMI between walk and vest tasks only. During the sled task, ACLR limb time to PKE torque predicted KEMI in the ACLR limb and PKE torque SI predicted KEMI SI.

Conclusion:

Women use asymmetrical KEMI profiles during all gait tasks, and those with worse KEMI during walking have worse KEMI during weighted gait. Men have asymmetrical KEMI when sled towing, and these KEMIs do not correlate with KEMI during walking or vest tasks.

Clinical Relevance:

PKE torque deficits persist when attempting to return to sports. Only men use gains in PKE torque to improve KEMI profiles. Although quicker PKE torque generation will increase KEMI in women, normalization of KEMI profiles will not occur by increasing rate of force development only. Gait retraining is recommended to correct asymmetrical KEMI profiles used across gait tasks in women.

Nanoengineered biomaterials for repair and regeneration of orthopedic tissue interfaces

Orthopedic interface tissue engineering aims to mimic the structure and function of soft-to-hard tissue junctions, particularly bone-ligament, bone-tendon, and bone-cartilage interfaces. A range of engineering approaches has been proposed to mimic the gradient architecture, physical properties and chemical characteristics of interface tissues using conventional polymeric biomaterials. Recent developments in nanomaterials and nanofabrication technologies introduce a range of synthesis and fabrication tools to effectively engineer the structure and function of native tissue interfaces. In this review, we will focus on nanoengineered strategies used to replicate the structural and functional aspects of native biological tissues for engineering bone-cartilage, bone-ligament, and bone-tendon interfaces. This review will also highlight some of the emerging applications and future potential of nanomaterials and fabrication technologies in engineering tissue interfaces.

STATEMENT OF SIGNIFICANCE

A major challenge in engineering interfaces is to control the physical and structural characteristics of an artificial environment. The use of nanomaterials and nanoengineered strategies allow for greater control over the changes in structure and function at molecular and nanometer length scale. This review focuses on advanced nanomaterials and nanofabrication approaches developed to emulate bone-cartilage, bone-ligament, and bone-tendon interface regions. Some of the emerging nanoengineered biomaterials proposed to mimic tissue interfaces are also highlighted.

Mapping current research trends on neuromuscular risk factors of non-contact ACL injury

The aim of this systematic review was (i) to identify neuromuscular markers that have been predictive of a primary non-contact ACL injury, (ii) to assess whether proposed risk factors have been supported or refuted in the literature from cohort and case-control studies, and (iii) to reflect on the body of research that aims at developing field based tools to assess risk through an association with these risk factors. Electronic searches were undertaken, of PubMed, SCOPUS, Web of Science, CINAHL and SPORTDiscus examining neuromuscular risk factors associated with ACL injury published between January 1990 and July 2015. The evidence supporting neuromuscular risk factors of ACL injury is limited where only 4 prospective cohort studies were found. Three of which looked into muscular capacity and one looked into muscular activation patterns but none of the studies found strong evidence of how muscular capacity or muscular activation deficits are a risk factor for a primary non-contact ACL injury. A number of factors associated to neural control and muscular capacity have been suggested to be related to non-contact ACL injury risk but the level of evidence supporting these risk factors remains often elusive, leaving researchers and practitioners uncertain when developing evidence-based injury prevention programs.

Impaired muscle function in a mouse surgical model of post-traumatic osteoarthritis

OBJECTIVES

Using a mouse surgical model of post-traumatic osteoarthritis (OA), we sought to determine if muscle function is altered following acute joint injury and whether this relates to OA progression.

DESIGN

Male C57BL/6 mice underwent surgical transection of the medio-meniscal tibial ligament destabilisation of the medial meniscus (DMM) or sham surgery on one knee. Tibialis anterior (TA) muscle function was assessed in situ at 1, 4 and 8 weeks post-surgery. Cartilage damage and joint inflammation were assessed by histologic scoring. Muscle mRNA expression was quantified by qRT-PCR.

RESULTS

Tetanic and twitch force production between DMM and sham muscle did not differ at 1 week post-surgery. Muscle function improved in both groups with time, but specific force production in DMM muscles was 18% and 22% lower than sham muscles at 4 and 8 weeks post-surgery respectively. At 8 weeks post-surgery, DMM muscles had a 40% slower relaxation rate and reduced expression of sarcoplasmic/endoplasmic reticulum Ca(2+) ATPase (Serca) pump mRNA compared to sham muscles; both observations indicate likely alterations in muscle Ca(2+) handling. There were no histologic signs of muscle atrophy or inflammation in DMM TA muscles. Specific force production in both sham and DMM mice showed a negative correlation with the severity of joint inflammation.

CONCLUSIONS

Acute knee injury in the DMM model of post-traumatic OA leads to a persistent deficit in TA muscle function that occurs in the absence of muscle atrophy. This study highlights that the impact of acute knee injury is unlikely to be limited to the muscles controlling knee movement.

Single- vs. double-bundle anterior cruciate ligament reconstruction: a new aspect of knee assessment during activities involving dynamic knee rotation

Few studies have compared single-bundle (SB) and double-bundle (DB) anterior cruciate ligament reconstruction (ACLR) in the knee joint during activities involving change-of-direction maneuvers and knee rotation. This study examined whether the type of ACLR contributes to postphysiotherapy outcomes, with an emphasis on knee function assessment during activities involving dynamic knee rotation. Fifteen male patients after SB ACLR and 15 male patients after DB ACLR took part in the same physiotherapy program. Twenty-four weeks after ACLR, both groups underwent anterior laxity measurement, pivot shift tests, range of movement and joint circumference measurements, subjective assessment of pain and stability levels in the knee joint, peak torque measurement of the muscles rotating the tibia toward the femur, and a run test with maximal speed and change-of-direction maneuvers. Comparative analysis did not show any differences between the results of anterior tibial translation, pivot shift test, range of movement and joint circumference, and subjective assessment of pain and knee joint stability levels. No differences were noted between the groups in peak torque values obtained from the muscles responsible for internal and external tibial rotation or results of the run test. The data obtained from this study can be used by research teams to monitor and compare the effectiveness of various study protocols involving surgical and physiotherapy treatment. The data are especially useful when combined with the clinical assessment of patients who would like to return to sport.

Effect of knee joint angle on side-to-side strength ratios

Isometric knee extensor and flexor strength are typically tested at different joint angles due to the differences in length-tension relationships of the quadriceps and hamstring muscles. The efficiency of strength testing can be improved if the same angle can be used to test both the knee extensor and flexor muscle groups. The aim of this study was to determine an optimal angle for isometric knee strength testing by examining the effect of knee angle on side-to-side peak torque ratios. Eighteen active young people (9 males and 9 females) participated in this study. Knee extensor and knee flexor strength were tested on both sides at 30°, 60°, and 90° of knee flexion. The effect of knee flexion angle on side-to-side peak torque ratios, raw torque values, and side-to-side flexor-to-extensor torque ratios were assessed. Side-to-side knee extensor peak torque ratios and knee flexor-to-extensor torque ratios differed significantly by knee flexion angle (p = 0.024 and p = 0.011, respectively), but side-to-side knee flexor peak torque ratios did not differ significantly (p = 0.311). When considering both side-to-side peak torque ratios and flexor-to-extensor torque ratios, the values were more symmetrical (i.e., closer to 100%) only at 60° of knee flexion. Our results indicate that both the knee flexors and the knee extensors can be tested clinically at 60° of knee flexion. Our results also indicate that the hamstrings can be tested at any of the 3 angles if the examiner is interested in side-to-side ratios rather than raw torque values. These results may facilitate more efficient and flexible clinical knee strength testing.

Deficits in Quadriceps Strength and Patient-Oriented Outcomes at Return to Activity After ACL Reconstruction: A Review of the Current Literature

Context:

Side-to-side quadriceps strength deficits are linked to hazardous lower extremity mechanics and reduced function at a time when individuals are returned to activity after anterior cruciate ligament (ACL) reconstruction. As a result, generalized criteria have emerged in the literature, wherein researchers are recommending that patients be cleared for participation once side-to-side differences in strength are ≤10% of the noninjured limb. Similar recommendations exist for patient-oriented outcomes (ie, self-reported function and hop tests), where deficits of ≤10% are considered ideal at return to activity. It is unclear how many studies actually achieve these clinically recommended results.

Evidence Acquisition:

Articles that reported quadriceps strength deficits as compared to the contralateral limb were collected from peer-reviewed sources available on Medline and Web of Science databases (1990 through August 2014). Search terms included the following: anterior cruciate ligament OR ACL AND muscle weakness, anterior cruciate ligament OR ACL AND strength; return-to-activity AND strength; anterior cruciate ligament OR ACL AND quadriceps.

Study Design:

Clinical review.

Level of Evidence:

Level 4.

Results:

Average side-to-side strength deficits at 6 months postreconstruction were 23% ± 8% (range, 3%-40%), while the average at 12 months postsurgery was found to be 14% ± 6% (range, 3%-28%). The average deficits in self-reported function at 6 months (mean, 14% ± 5%) and 12 months postsurgery (mean, 13% ± 6%) were also found to be >10%. Performance on hop tests was found to be less than optimal at 6 months postsurgery (mean, 11% ± 7%), but improved at 12 months postsurgery (mean, 1.3% ± 2%).

Conclusion:

This review provides an up-to-date account of the typical deficits in strength and patient-oriented outcomes that exist when formalized physical therapy concludes after ACL reconstruction. Based on the studies included, it seems pertinent that researchers and clinicians continue to investigate interventions capable of improving the recovery of quadriceps strength as well as patient-oriented outcomes as the majority of studies report levels that are well below clinical recommendations.

The Relationship between Anterior Cruciate Ligament Injury and Osteoarthritis of the Knee

Anterior cruciate ligament (ACL) tears are a common injury, particularly in the athletic and youth populations. The known association between ACL injury and subsequent osteoarthritis (OA) of the knee merits a more in-depth understanding of the relationship between the ACL-injured knee and osteoarthritis. ACL injury, especially with concomitant meniscal or other ligamentous pathology, predisposes the knee to an increased risk of osteoarthritis. ACL insufficiency results in deterioration of the normal physiologic knee bending culminating in increased anterior tibial translation and increased internal tibial rotation. This leads to increased mean contact stresses in the posterior medial and lateral compartments under anterior and rotational loading. However, surgical reconstruction of the ACL has not been shown to reduce the risk of future OA development back to baseline and has variability based on operative factors of graft choice, timing of surgery, presence of meniscal and chondral abnormalities, and surgical technique. Known strategies to prevent OA development are applicable to patients with ACL deficiency or after ACL reconstruction and include weight management, avoidance of excessive musculoskeletal loading, and strength training. Reconstruction of the ACL does not necessarily prevent osteoarthritis in many of these patients and may depend on several external variables.

What can the first 2 months tell us about outcomes after anterior cruciate ligament reconstruction?

CONTEXT

Substantial research has been conducted on anterior cruciate ligament reconstruction (ACLR) to evaluate patient outcomes. However, little attention has been given to outcomes during the early phase of recovery and how early deficits affect both short- and long-term outcomes.

OBJECTIVE

To identify relationships between demographic (age, sex, and body mass index [BMI]) and intraoperative (isolated ACLR versus primary ACLR + secondary procedures), and postoperative (range-of-motion [ROM] and peak isometric knee-extension force [PIF]) variables during the first 2 months after ACLR using self-reported outcomes.

DESIGN

Cohort study.

SETTING

Outpatient orthopaedic hospital.

PATIENTS OR OTHER PARTICIPANTS

A total of 63 patients (38 men, 25 women; age = 33.0 ± 12.1 years; BMI = 26.3 ± 6.5 kg/m(2)) who underwent ACLR.

MAIN OUTCOME MEASURE(S)

Demographic, intraoperative, and postoperative variables were collected at 1 and 2 months after ACLR and were compared with International Knee Documentation Committee (IKDC) Subjective Knee Evaluation Form scores at 1, 2, and ≥12 months.

RESULTS

Significant relationships were identified between ≥12-month IKDC scores and the 1-month (Pearson correlation, r = 0.283, r(2) = 0.08; P = .025) and 2-month (r = 0.301, r(2) = 0.09; P = .017) IKDC scores. After controlling for other variables, we found that the PIF ratio measures at 1 and 2 months were positively associated with 1- and 2-month IKDC scores (P < .001) and BMI was negatively associated with both 1- and 2-month IKDC scores (P < .05). One-month IKDC scores were related to the 1-month difference in knee-flexion ROM (P = .04).

CONCLUSIONS

The IKDC scores during the first 2 months were positively correlated with patients' perceptions of function on long-term IKDC scores. It also appears that improvements in lower extremity strength and flexion ROM deficits were positively associated with short-term IKDC scores. Higher BMI was negatively associated with patients' perceptions of function on short-term IKDC scores.