Long-term deficits in quadriceps strength and activation following anterior cruciate ligament reconstruction

Longitudinal changes in adiposity following anterior cruciate ligament reconstruction and associations with knee symptoms and function

Objective

To evaluate adiposity after anterior cruciate ligament reconstruction (ACLR): i) cross-sectionally (1-year post-ACLR) compared to uninjured controls; ii) longitudinally up to 5 years post-ACLR; and iii) associations with patient-reported symptoms and physical performance.

Methods

In 107 individuals post-ACLR and 19 controls, we assessed global (BMI), peripheral (subcutaneous adipose tissue thickness on the posteromedial side of knee MRI), and central (waist circumference in ACLR group) adiposity. Patient-reported symptoms (Knee injury and Osteoarthritis Outcome Score) and physical performance (hop for distance) were evaluated at 1 and 5 years post-ACLR. Linear regression models evaluated adiposity between groups. Paired t-tests evaluated changes in adiposity from 1- to 5 years post-ACLR. Linear regression models analyzed adiposity's associations with patient-reported symptoms and physical performance at 1-year post-ACLR, changes in symptoms and performance over 4 years post-ACLR, and longitudinal changes in adiposity and symptoms and performance, controlling for age, sex, and activity level.

Results

Individuals 1-year post-ACLR were associated with higher average global (3 ​kg/m2) and peripheral adiposity (2.3 ​mm). From 1- to 5 years post-ACLR, higher average global (0.58 ​kg/m2) and central (5 ​cm) adiposity, and lower average peripheral adiposity (1.3 ​mm) were observed. In general, adiposity at one-year post-ACLR was negatively associated with patient-reported symptoms and physical performance, and changes from 1 to 5 years post-ACLR. Increases in adiposity were negatively associated with changes in patient-reported symptoms and physical performance over four years post-ACLR.

Conclusion

Greater global and central adiposity is a feature of young adults following ACLR and influences current and future patient-reported symptoms and physical performance.

The nature of gait biomechanics changes with walking speed increase in patients with anterior cruciate ligament injury

BACKGROUND

This study on gait biomechanics is based on a functional test (FT) performed at free and fast walking speeds.

OBJECTIVE

We investigated the pattern of changes in gait biomechanical parameters and the knee function in patients after anterior cruciate ligament (ACL) injury or its reconstruction.

METHODS

The study included 51 patients (33 males, 18 females) with a confirmed recent or old history of ACL tear, before or after reconstruction (26 patients). Mocap data was obtained using an inertial system. All patients were divided into three groups: 41 patients with physiological response (compensation), 6 patients with signs of decompensation, and 4 non-assessable patients.

RESULTS

Increase in gait speed was associated with decrease in the walking cycle duration, stance and double support phases. In the compensation group, the physiological response of the knee was manifested in increased amplitudes. In the decompensation group, the amplitudes remained unchanged or decreased. In the compensation group, there were increases in the symmetrical muscle activity. The decompensation group was characterized by electromyography asymmetry.

CONCLUSION

The observed universal physiological mechanism limiting the load on the damaged joint can be used for accurate assessment of the knee functional state in various periods of rehabilitation.

Ingersoll C, E. Norte G. Neural drive and motor unit characteristics after anterior cruciate ligament reconstruction: implications for quadriceps weakness

Purpose

The purpose of this investigation was to compare the quality of neural drive and recruited quadriceps motor units' (MU) action potential amplitude (MUAPAMP) and discharge rate (mean firing rate (MFR)) relative to recruitment threshold (RT) between individuals with anterior cruciate ligament reconstruction (ACLR) and controls.

Methods

Fourteen individuals with ACLR and 13 matched controls performed trapezoidal knee extensor contractions at 30%, 50%, 70%, and 100% of their maximal voluntary isometric contraction (MVIC). Decomposition electromyography (dEMG) and torque were recorded concurrently. The Hoffmann reflex (H-reflex) and central activation ratio (CAR) were acquired bilaterally to detail the proportion of MU pool available and volitionally activated. We examined MUAPAMP-RT and MFR-RT relationships with linear regression and extracted the regression line slope, y-intercept, and RT range for each contraction. Linear mixed effect modelling used to analyze the effect of group and limb on regression line slope and RT range.

Results

Individuals with ACLR demonstrated lower MVIC torque in the involved limb compared to uninvolved limb. There were no differences in H-reflex or CAR between groups or limbs. The ACLR involved limb demonstrated smaller mass-normalized RT range and slower MU firing rates at high contraction intensities (70% and 100% MVIC) compared to uninvolved and control limbs. The ACLR involved limb also demonstrated larger MU action potentials in the VM compared to the contralateral limb. These differences were largely attenuated with relative RT normalization.

Conclusions

These results suggest that persistent strength deficits following ACLR may be attributable to a diminished quadriceps motor neuron pool and inability to upregulate the firing rate of recruited MUs.

Recurrence quantification analysis of isokinetic strength tests: A comparison of the anterior cruciate ligament reconstructed and the uninjured limb

BACKGROUND

Despite widespread use of return to sport testing following anterior cruciate ligament reconstruction, studies suggest inadequacy in current testing criteria, such as limb symmetry index calculations, to determine athletes' readiness to return to play. Recurrence quantification analysis, an emerging non-linear data analysis tool, may reveal subtle neuromuscular differences between the injured and uninjured limb that are not captured by traditional testing. We hypothesized that isokinetic torque curve data of the injured limb would demonstrate lower determinism and entropy as compared to the uninjured limb.

METHODS

102 patients (44 M, 58F, 10 ± 1 months post-anterior cruciate ligament reconstruction) underwent isokinetic quadriceps strength testing using a HumacNorm dynamometer. Patients completed maximum effort knee extension and flexion at 60°/sec. Data were post-processed with a MATLAB CRQA Graphical User Interface and determinism and entropy values were extracted. Paired-sample t-tests (α = 0.05) were used to compare data from the injured and uninjured limb.

FINDINGS

Determinism and entropy values in the torque curves were lower in the injured limb than the uninjured limb (p < 0.001). Our findings indicate there is less predictability and complexity present in the torque signals of injured limbs.

INTERPRETATION

Recurrence quantification analysis can be used to assess neuromuscular differences between limbs in patients who have undergone anterior cruciate ligament reconstruction. Our findings offer further evidence that there are changes to the neuromuscular system which persist following reconstruction. Further investigation is needed to establish thresholds of determinism and entropy values needed for safe return to sport and to evaluate the utility of recurrence quantification analysis as a return to sport criterion.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

TRIAL REGISTRATION

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

Evaluation of raw segmental bioelectrical impedance variables throughout anterior cruciate ligament reconstruction rehabilitation

Background.Raw bioelectrical impedance analysis (BIA) variables are related to physical function in healthy and diseased populations. Therefore, BIA may be an insightful, noninvasive method of assessment to track following anterior cruciate ligament reconstruction (ACLR).Objectives.Evaluate phase angle, reactance and impedance at 50 kHz (PhA₅₀, Xc₅₀, andZ₅₀, respectively) in the operative (OP) and non-operative (NOP) limbs during ACLR rehabilitation.Approach.Seventeen patient (12 M, 5 F; 18.8 ± 4.8 years) clinic reports were evaluated prior to ACLR (PRE), two- (2 W), six- (6 W), and twelve-weeks (12 W) post-ACLR and at return to sport testing (RTS).Setting.All observations occurred during the participant's physical therapy visits.Measurements.A multi-frequency BIA device measured segmental PhA, Xc, andZ. Linear mixed effects models were used to assess any leg and time interaction and changes over leg and time, independently. Any interactions or main effects were considered significant atp< 0.05.Main results.Significant legxtime interactions were observed for each variable. PhA₅₀and Xc₅₀of NOP were higher (p< 0.001) than OP at each time point by an average of by 0.9° and 4.9 Ω, respectively. In OP, PhA₅₀and Xc₅₀decreased from PRE to 2 W and increased from 6 to 12 W and 12 W to RTS (p< 0.01, for all). At RTS, PhA₅₀and Xc₅₀were similar to PRE in OP (p> 0.05). ForZ₅₀, the OP leg did not change over time (p> 0.05).Z₅₀was greater in NOP at 2 and 6 W (p< 0.01, for both). There were differences in PhA₅₀in NOP between PRE and 6 W and from 6 W to RTS (p< 0.05 for both). Xc₅₀did not change (p> 0.05), andZ₅₀PRE was lower than at 2 W (p< 0.05).Significance.A multi-frequency BIA device can detect changes in segmental BIA variables following ACLR.

Effects of 8-Week Exhausting Deep Knee Flexion Flywheel Training on Persistent Quadriceps Weakness in Well-Trained Athletes Following Anterior Cruciate Ligament Reconstruction

Persistent quadriceps weakness after anterior cruciate ligament (ACL) reconstruction is a common hurdle to efficient rehabilitation. Therefore, we evaluated a new treatment strategy for athletes with ACL reconstruction. Eleven athletes with unilateral ACL reconstruction performed one set of flywheel Bulgarian split squats to exhaustion with a maximum knee extension of 60°, over 16 sessions, on their reconstructed limb. Quadriceps rate of force development (RFD) 0-50 ms (RFD_{0-50 ms}), and 0-150 ms (RFD_{0-150 ms}), maximum voluntary isometric contraction (MVIC), and central activation ratio (CAR) were measured bilaterally on the week before and after the intervention. In the reconstructed limb, the RFD_{0-50 ms} (p = 0.04; Cohen's d = 0.8) and RFD_{0-150 ms} (p = 0.03; d = 0.9) increased after training. Before-after changes in MVIC and CAR were not significant (p > 0.05), but the lower the baseline MVIC, the greater the gain in MVIC (r = -0.71, p = 0.02). The between-leg difference in MVIC changed from large before (p = 0.01; d = 0.8) to small after training (p = 0.04; d = 0.4). One set of deep knee flexion flywheel Bulgarian split squats to exhaustion improved quadriceps deficits in well-trained athletes with ACL-reconstruction, particularly those with relatively low quadriceps force production.

Anterior-cruciate-ligament reconstruction does not alter the knee-extensor moment arm during gait

BACKGROUND

The ability of the quadriceps muscles to extend the knee depends on the moment arm of the knee-extensor mechanism, which is described by the moment arm of the patellar tendon at the knee. The knee-extensor moment may be altered by a change in quadriceps force, a change in the patellar tendon moment arm (PTMA), or both. A change in quadriceps muscle strength after anterior-cruciate-ligament-reconstruction (ACLR) surgery is well documented, however, there is limited knowledge about how this procedure affects the PTMA.

RESEARCH QUESTION

Does ACLR surgery alter the moment arm of the knee-extensor mechanism during gait?

METHODS

We measured the PTMA in both the ACLR knee and the uninjured contralateral knee in 10 young active individuals after unilateral ACLR surgery. Mobile biplane X-ray imaging was used to measure the three-dimensional positions of the femur, tibia and patella during level walking and downhill walking over ground. The PTMA was found from the location of the instantaneous axis of rotation at the knee and the line-of-action of the patellar tendon.

RESULTS

There was a small but statistically significant difference in the mean PTMA calculated over one cycle of level walking between the ACLR knee and the contralateral knee, with the mean PTMA in the ACLR knee being 1.5 mm larger (p < 0.01). In downhill walking, statistically significant differences were found in the range 15°- 25° of knee flexion, where the PTMA was 4.7 mm larger in the ACLR knee compared to the contralateral knee (p < 0.01).

SIGNIFICANCE

Significant differences were evident in the mean PTMA between the ACLR knee and the contralateral knee in both activities, however, the magnitudes of these differences were relatively small (range: 3-10%), indicating that ACLR surgery successfully restores the moment arm of the knee-extensor mechanism during dynamic activity.

Bilateral Alterations in Isokinetic Strength and Knee Biomechanics During Side-Cutting 1 Year After Unilateral ACL Reconstruction

BACKGROUND

Individuals with anterior cruciate ligament (ACL) reconstruction (ACLR) are a population that has a higher risk for ACL injury compared with the general population. To reduce the reinjury rate and improve the rehabilitation outcome after ACLR, risk factors for ACL injury have to be addressed.

PURPOSE

To compare the knee biomechanics during side-cutting and isokinetic strength of the thigh muscle of the reconstructed leg with those of the contralateral leg and healthy controls and investigate the knee movement asymmetries in individuals with ACLR.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 16 participants with ACLR (ACLR group; 11.8 ± 1.1 months after reconstruction) and 16 healthy controls (control group) were recruited. Landmark coordinates and ground-reaction forces during side-cutting and isokinetic strength of hamstring and quadriceps were collected. Two-way analysis of variance with the mixed design was performed to compare each dependent variable between groups and across legs.

RESULTS

The reconstructed leg had a significantly smaller knee flexion angle (P = .004) and less quadriceps strength (P = .003) than the contralateral leg. The knee extension moment and knee external rotation angle were decreased compared with both the contralateral leg (P = .001, P = .003, respectively) and the healthy control leg (P = .001, P = .001, respectively). The ACLR group showed greater knee abduction angles (P = .004) and smaller knee external rotation moments (P = .006) than the control group. The ACLR group also demonstrated greater asymmetries of knee flexion angle (P = .015), knee external rotation angle (P = .001), knee extension moment (P = .013), knee abduction moment (P = .001), and quadriceps strength (P = .046) than the control group.

CONCLUSION

Knee biomechanics in the leg with ACLR were altered mainly in the sagittal plane during side-cutting compared with the contralateral leg. The altered movement patterns between the ACLR and control groups were primarily observed in the frontal and transverse planes. The ACLR group also demonstrated greater asymmetries of sagittal knee movement and concentric quadriceps strength than the control group.

CLINICAL RELEVANCE

Individuals with ACLR showed different alterations in the reconstructed and contralateral leg compared with healthy controls. These results suggest that rehabilitation programs after ACLR should further focus on restoring the knee flexion angle and quadriceps strength. Injury prevention programs need to be further targeted in the altered movement patterns observed between the ACLR and the healthy groups.

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

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

The relationship between knee loading during gait and cartilage thickness in nontraumatic and posttraumatic knee osteoarthritis

The relationship between knee moments and markers of knee osteoarthritis progression has not been examined in different knee osteoarthritis subtypes. The objective was to examine relationships between external knee moments during gait and tibiofemoral cartilage thickness in patients with nontraumatic and posttraumatic knee osteoarthritis. For this cross-sectional study, participants with knee osteoarthritis were classified into two groups: nontraumatic (n = 22; mean age 60 years) and posttraumatic (n = 19; mean age 56 years, history of anterior cruciate ligament rupture). Gait data were collected with a three-dimensional motion capture system sampled at 100 Hz and force plates sampled at 2000 Hz. External knee moments were calculated using inverse dynamics. Cartilage thickness was determined with magnetic resonance imaging (T1-weighted, 3D sagittal gradient-echo sequence). Linear regression analyses examined relationships between cartilage thickness with knee moments, group, and their interaction. A higher knee adduction moment impulse was negatively associated with medial to lateral cartilage thickness ratio (B = -1.97). This relationship differed between participants in the nontraumatic osteoarthritis group (r = -0.56) and posttraumatic osteoarthritis group (r = -0.30). A higher late stance knee extension moment was associated with greater medial femoral condyle cartilage thickness (B = -0.86) and medial to lateral cartilage thickness (B = -0.73). These relationships also differed between participants in the nontraumatic osteoarthritis group (r = -0.61 and r = -0.51, respectively) and posttraumatic osteoarthritis group (r = 0.10 and r = 0.25, respectively). Clinical Significance: The relationship between knee moments with tibiofemoral cartilage thickness differs between patients with nontraumatic and posttraumatic knee osteoarthritis. The potential influence of mechanical knee loading on articular cartilage may also differ between these subtypes.

Risk Factors Associated with Cartilage Defects after Anterior Cruciate Ligament Rupture in Military Draftees

This study aimed to evaluate the different clinical results and factors associated with cartilage defects in military draftees who underwent different treatments after anterior cruciate ligament (ACL) rupture. Overall, 105 patients who had sustained ACL rupture were military draftees who underwent a conscription examination for physical status assessment from January 2012 to December 2020. Patients were divided into three groups: conservative treatment after ACL rupture, status post-anterior cruciate ligament reconstruction (ACLR), but graft rupture, and status post-ACLR with graft intact. Inter-group comparisons and statistical analyses were performed for age, body mass index (BMI), thigh circumference difference, side-to-side difference in anterior knee translation by KT-2000, meniscus tear, and cartilage defect. Multivariate logistic regression analysis was used to determine the factors associated with cartilage defects. The multivariable regression model showed that BMI (odds ratio OR: 1.303; 95% CI: 1.016–1.672; p = 0.037), thigh circumference difference (OR: 1.403; 95% CI: 1.003–1.084; p = 0.034), tear of lateral meniscus (LM) and medial meniscus (MM) (OR: 13.773; 95% CI: 1.354–140.09; p = 0.027), and graft rupture group (OR: 5.191; 95% CI: 1.388–19.419; p = 0.014) increased the risk of cartilage defects. There was no correlation between cartilage defects and age, KT-2000 difference, tear of LM or MM, or graft intact group. Progression of osteoarthritis was concerned after ACL rupture, and this study identified several factors of post-ACLR graft rupture, greater thigh circumference difference, BMI, and meniscus tear of both LM and MM affecting cartilage defects, which represent early degenerative osteoarthritis changes of the knee. The results of this study should be customized for rehabilitation and military training, especially in military draftees with ACL injuries.

Lower-Limb Muscle Activity During Aquatic Treadmill Running in Individuals With Anterior Cruciate Ligament Reconstruction

INTRODUCTION

While anterior cruciate ligament (ACL) tears are commonly managed with ACL reconstruction (ACL-R), 35% of ACL-R individuals fail to return to the preinjury elite sport level. Persistent neuromuscular deficits in the hamstrings and quadriceps have been observed. It has been proposed that aquatic therapy can be used to optimize neuromuscular control after ACL-R.

OBJECTIVES

(1) To compare muscle activity in ACL-R individuals during aquatic treadmill (ATM) running at different water depths and (2) to compare muscle activity during ATM running between ACL-R and healthy individuals.

METHODS

A total of 38 participants, including 18 ACL-R individuals (mean postoperative time [SD] = 25.8 [25.0] mo) and 20 healthy individuals were recruited. Muscle activity of biceps femoris (BF), rectus femoris (RF), tibialis anterior, and medial gastrocnemius during land treadmill and ATM running at mid-shin, mid-thigh, and waist levels were recorded using surface electromyography (sEMG).  The sEMG signals of the selected muscles were normalized and expressed in % Maximal Voluntary Contraction (%MVC). Muscle activity of the ACL-R, ACL-contralateral, and healthy control limbs at different water depths was compared.

RESULTS

Among the 3 groups, the ACL-R group demonstrated the most prominent percentage increase of 101.97% (P = .001) at mid-shin level, 139.66% (P = .001) at mid-thigh level, and 141.97% (P < .001) at waist level, respectively, in %MVC when compared to land. In the ACL-R group, muscle activity of BF in the stance phase (BFSt) was significantly higher than the control group on land at all water depths. Muscle activity of RF in the swing phase (RFSw) in the ACL-R group significantly increased in all water depths immersion when compared to land, respectively.

CONCLUSION

This study showed an increasing trend in muscle activity of BFSt and RFSw in ACL-R individuals during ATM running at increased water depths. ATM running could be implemented as neuromuscular training in rehabilitation after ACL-R.

Long-Lasting Impairments in Quadriceps Mitochondrial Health, Muscle Size, and Phenotypic Composition Are Present After Non-invasive Anterior Cruciate Ligament Injury

Introduction

Despite rigorous rehabilitation aimed at restoring muscle health, anterior cruciate ligament (ACL) injury is often hallmarked by significant long-term quadriceps muscle weakness. Derangements in mitochondrial function are a common feature of various atrophying conditions, yet it is unclear to what extent mitochondria are involved in the detrimental sequela of quadriceps dysfunction after ACL injury. Using a preclinical, non-invasive ACL injury rodent model, our objective was to explore the direct effect of an isolated ACL injury on mitochondrial function, muscle atrophy, and muscle phenotypic transitions.

Methods

A total of 40 male and female, Long Evans rats (16-week-old) were exposed to non-invasive ACL injury, while 8 additional rats served as controls. Rats were euthanized at 3, 7, 14, 28, and 56 days after ACL injury, and vastus lateralis muscles were extracted to measure the mitochondrial respiratory control ratio (RCR; state 3 respiration/state 4 respiration), mitochondrial reactive oxygen species (ROS) production, fiber cross sectional area (CSA), and fiber phenotyping. Alterations in mitochondrial function and ROS production were detected using two-way (sex:group) analyses of variance. To determine if mitochondrial characteristics were related to fiber atrophy, individual linear mixed effect models were run by sex.

Results

Mitochondria-derived ROS increased from days 7 to 56 after ACL injury (30–100%, P &lt; 0.05), concomitant with a twofold reduction in RCR (P &lt; 0.05). Post-injury, male rats displayed decreases in fiber CSA (days 7, 14, 56; P &lt; 0.05), loss of IIa fibers (day 7; P &lt; 0.05), and an increase in IIb fibers (day 7; P &lt; 0.05), while females displayed no changes in CSA or phenotyping (P &gt; 0.05). Males displayed a positive relationship between state 3 respiration and CSA at days 14 and 56 (P &lt; 0.05), while females only displayed a similar trend at day 14 (P = 0.05).

Conclusion

Long-lasting impairments in quadriceps mitochondrial health are present after ACL injury and play a key role in the dysregulation of quadriceps muscle size and composition. Our preclinical data indicate that using mitoprotective therapies may be a potential therapeutic strategy to mitigate alterations in muscle size and characteristic after ACL injury.

Effects of Deficits in the Neuromuscular and Mechanical Properties of the Quadriceps and Hamstrings on Single-Leg Hop Performance and Dynamic Knee Stability in Patients After Anterior Cruciate Ligament Reconstruction

Background:

Understanding the role of neuromuscular and mechanical muscle properties in knee functional performance and dynamic knee stability after anterior cruciate ligament reconstruction (ACLR) may help in the development of more focused rehabilitation programs.

Purpose:

To compare the involved and uninvolved limbs of patients after ACLR in terms of muscle strength, passive muscle stiffness, muscle activation of the quadriceps and hamstrings, hop performance, and dynamic knee stability and to investigate the association of neuromuscular and mechanical muscle properties with hop performance and dynamic knee stability.

Study Design:

Cross-sectional study; Level of evidence, 3.

Method:

The authors studied the quadriceps and hamstring muscles in 30 male patients (mean ± SD age, 25.4 ± 4.1 years) who had undergone unilateral ACLR. Muscle strength was measured using isokinetic testing at 60 and 180 deg/s. Passive muscle stiffness was quantified using ultrasound shear wave elastography. Muscle activation was evaluated via electromyographic (EMG) activity. Hop performance was evaluated via a single-leg hop test, and dynamic knee stability was evaluated via 3-dimensional knee movements during the landing phase of the hop test.

Results:

Compared with the uninvolved limb, the involved limb exhibited decreased peak torque and shear modulus in both the quadriceps and hamstrings as well as delayed activity onset in the quadriceps (P < .05 for all). The involved limb also exhibited a shorter hop distance and decreased peak knee flexion angle during landing (P < .05 for both). Decreased peak quadriceps torque at 180 deg/s, the shear modulus of the semitendinosus, and the reactive EMG activity amplitude of the semimembranosus were all associated with shorter hop distance (R² = 0.565; P < .001). Decreased quadriceps peak torque at 60 deg/s and shear modulus of the vastus medialis were both associated with smaller peak knee flexion angle (R² = 0.319; P < .001).

Conclusion:

In addition to muscle strength deficits, deficits in passive muscle stiffness and muscle activation of the quadriceps and hamstrings were important contributors to poor single-leg hop performance and dynamic knee stability during landing. Further investigations should include a rehabilitation program that normalizes muscle stiffness and activation patterns during landing, thus improving knee functional performance and dynamic knee stability.

Gait asymmetries are exacerbated at faster walking speeds in individuals with acute anterior cruciate ligament reconstruction

Previous research suggests more biomechanically demanding tasks (e.g., stair descent, hopping) magnify biomechanical asymmetries compared with walking after anterior cruciate ligament (ACL) reconstruction. However, it is unclear if modifying task-specific constraints, like walking speed also elicits greater biomechanical asymmetries in this population. We examined the effects of manipulating walking speed on ground reaction force (GRF) asymmetries in individuals with ACL reconstruction and uninjured controls. Thirty individuals with ACL reconstruction (age = 20.6 ± 5.4 years, body mass index [BMI] = 23.9 ± 3.3 kg/m2 ) and 15 controls (age = 23.1 ± 4.5 years, BMI = 23.6 ± 2.7 kg/m2 ) were tested on an instrumented treadmill at three speeds (100%, 120%, and 80% self-selected speed). Bilateral vertical and posterior-anterior GRFs were recorded at each speed. GRF asymmetries were calculated by subtracting the uninjured from the injured limb at each percent of stance. Statistical parametric mapping was used to evaluate the effects of speed on GRF asymmetries across stance. We found vertical and posterior GRF asymmetries were exacerbated at faster speeds and reduced at slower speeds in ACL individuals but not controls (p < .05). No differences in anterior GRF asymmetries were observed between speeds in either group (p > .05). Our results suggest increasing walking speed magnifies GRF asymmetries in individuals with ACL reconstruction. Statement of Clinical Significance: Evaluating both preferred and fast walking speeds may aid in characterizing biomechanical asymmetries in individuals with ACL reconstruction which may be valuable in earlier rehabilitative time points when more difficult tasks like hopping and running are not feasible.

Decreased passive muscle stiffness of vastus medialis is associated with poorer quadriceps strength and knee function after anterior cruciate ligament reconstruction

BACKGROUND

Muscle deficits of the quadriceps and hamstrings are common after anterior cruciate ligament reconstruction, and increase the risk of knee reinjury. Muscle stiffness is an important factor for dynamic joint stability. However, the changes in quadriceps and hamstring muscle stiffness and its influence after anterior cruciate ligament reconstruction remain unclear.

METHOD

Twenty-five male subjects with anterior cruciate ligament reconstruction and twenty-one matched healthy subjects participated in this study. The passive muscle stiffness of the quadriceps and hamstrings was assessed by shear modulus using ultrasound shear wave elastography. The isokinetic muscle strengths of the quadriceps and hamstrings were tested. Knee function was evaluated by the International Knee Documentation Committee and Lysholm score. Muscle stiffness was compared between limbs via non-parametric tests. Correlation analysis was used to detect the relationship between muscle stiffness, isokinetic muscle strength and knee functional scores.

FINDINGS

The involved limb exhibited significantly decreased shear modulus in the vastus medialis compared to the dominant limbs(z = -3.585;P = 0.001;ES = 1.13) and non-dominant limbs(z = -3.551;P = 0.002;ES = 1.24) of healthy controls. The shear modulus of ST was also significantly lower in the involved limb when compared with the contralateral limbs(z = -3.996;P < 0.001;ES = 1.33), dominant limbs(z = -4.477;P < 0.001;ES = 1.65) and non-dominant limbs(z = -4.234;P = 0.001;ES = 1.43) of healthy controls. The shear modulus of the vastus medialis was associated with quadriceps peak torque at 60°/s(r = 0.470; p < 0.001) and knee functional score(r = 0.459; p = 0.021).

INTERPRETATION

The passive muscle stiffness of the vastus medialis decreased after anterior cruciate ligament reconstruction, which is associated with poorer quadriceps strength and knee function. The effect of modulation of muscle stiffness on improving knee function warrants future investigation.

Examining the Relationship Between Neuroplasticity and Learned Helplessness After ACLR: Early Versus Late Recovery

Context: Altered neural signaling is known to have a direct impact on psychological wellness. Therefore, disruptions in neural signaling after anterior cruciate ligament reconstruction may influence psychological dysfunction, in some cases manifesting as learned helplessness. Helplessness is a psychological paradigm that presents as altered neuromuscular control, reduced motivation, and psychological deficits. Objectives: The authors sought to evaluate the relationship between helplessness, neural activity, and quadriceps function at different time points after anterior cruciate ligament reconstruction. Evidence Acquisition: Twenty-nine individuals with unilateral anterior cruciate ligament reconstruction were categorized into early group (<2 y, age: 19.13 [2.18] y; height: 1.77 [0.11] m; mass: 76.903 [11.87] kg) or late group (>2 y, age: 22 [23] y; height: 1.67 [0.07] m; mass: 65.66 [11.33] kg). Quadriceps function (activation and strength), spinal-reflexive and corticospinal excitability (active motor thresholds and motor evoked potentials), and helplessness were obtained. A principal component analysis was performed by group (early and late) to identify which factors of helplessness were most associated with neural activity and quadriceps function. Pearson product moment correlation analyses were performed by group to determine associations between individual components and main outcomes. Evidence Synthesis: In the early group, cognitive readiness was associated with quadriceps strength of the injured limb (r2 = .513, P = .004), and self-awareness/management was associated with motor threshold of the injured limb (r2 = .238, P = .05). In the late group, intrinsic helplessness was associated with motor output of injured limb (r2 = .653, P = .01). Conclusion: Helplessness is made up of several attributional constructs, which are altered at different phases of recovery. Helplessness constructs interact differently with neural activity and quadriceps function across time. These findings are preliminary and do not establish a causal link between neural alterations and learned helplessness. Future studies should serially evaluate both changes in neural activity and learned helplessness attributes throughout recovery.

Type of measurement used influences central and peripheral contributions to quadriceps weakness after anterior cruciate ligament (ACL) reconstruction

OBJECTIVE

The relative contribution of muscle size and voluntary activation (VA) on quadriceps strength after anterior cruciate ligament (ACL) reconstruction remains inconclusive. Here, we aimed to determine the contributions of muscle size and VA on quadriceps strength in ACL-reconstructed patients and determine if contributions were similar if unilateral outcomes (i.e. ACL-reconstructed limb) or the LSI was used.

DESIGN

A cross-sectional study.

SETTING

A university research laboratory.

PARTICIPANTS

Sixteen individuals 6-12 months after ACL reconstruction (Age: 22.3 ± 6.0yr, Height: 1.7 ± 0.1 m, Mass: 68.7 ± 11.5 kg) were recruited.

MAIN OUTCOME MEASURES

Quadriceps isometric strength and VA, via the interpolated triplet technique, were assessed bilaterally. Ultrasound images were acquired of the vastus lateralis to calculate cross-sectional area (CSA) in both legs. LSI's were computed for all variables by expressing values of the reconstructed leg as a percent of the non-reconstructed leg. Separate stepwise linear regressions were performed to examine the contribution of VA and CSA on quadriceps strength. Model 1 used LSI for all outcomes and model 2 used outcomes from the reconstructed leg.

RESULTS

We observed between limb deficits of 27.78% in quadriceps strength, 13.61% in vastus lateralis CSA, and 13.18% in VA (P < 0.05). Strength LSI was significantly predicted by VA LSI (R² = 0.45, P < 0.01), but not by CSA LSI (R² = 0.01, P =0.87). Reconstructed leg strength was significantly predicted by VL CSA (R² = 0.50, P < 0.01) but not quadriceps VA (R² = 0.08, P =0.11).

CONCLUSIONS

The contributions of VA and CSA on quadriceps PT differed greatly if LSI or reconstructed leg outcomes were used. Evaluation of VA and CSA in unison may be provide a more holistic understanding of the sources of muscle weakness after ACL reconstruction.

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.

Physical Fitness after Anterior Cruciate Ligament Reconstruction: Influence of Graft, Age, and Sex

Functional tests are used to facilitate return-to-sports decisions after anterior cruciate ligament reconstruction (ACLR). This study presents comprehensive physical fitness test data acquired in highly active patients within the first year after ACLR, for comparison between different grafts, age groups, and sexes. The outcomes from a specific seven-item test battery and isokinetic strength test data were extracted from a patient database. Results were compared to normative data from age- and sex-matched controls and between subgroups of patients. A total of 245 patients (94 women, 23.8 ± 8.4 years, pre-injury Tegner 7.4 ± 1.6) were tested 185 ± 44 days after surgery. In 116 patients (47.3%), one or more test results were classified as "poor" or "very poor" after comparison with normative data, with failures being most frequent during single-leg squat jump and plyometric strength tests. Test failures were more prevalent in adults than in adolescents <19 years (61.4%-62.2% vs. 24.5%, p < 0.001) and in men (61.6% vs. 24.5%, p < 0.001), but no differences were found between grafts. Isokinetic knee extensor strength was lower by 24.1% on the injured side. Six months after ACLR, nearly 50% of highly active patients presented with strength and functional fitness deficits. These deficits are particularly prevalent in older patients and men.

[Effect of isokinetic training of thigh muscle group on graft remodeling after anterior cruciate ligament reconstruction]

Objective

To investigate the effect of isokinetic training of thigh muscle group on graft remodeling after anterior cruciate ligament (ACL) reconstruction, and summarize the relevant rules to guide the clinic.

Methods

Between August 2016 and December 2016, forty patients underwent arthroscopic ACL reconstruction using hamstring tendon were randomly divided into isokinetic group and control group ( n=20). The two groups of patients underwent staged rehabilitation treatment. The isokinetic group replaced the traditional intervention with the corresponding isokinetic strength training from 3 to 6 months after operation, and the traditional rehabilitation intervention was used in the control group. Finally, 12 cases of isokinetic group and 12 cases of control group with complete follow-up were enrolled in study. There was no significant difference in gender, age, body mass index, side of injury, the interval between injury and operation, and preoperative International Knee Documentation Committee (IKDC) score between the two groups ( P>0.05). The peak torque (PT) of knee extension and flexion and hamstring quadriceps ratio (H/Q) were measured at 3 months, 6 months, 12 months, and the second-look arthroscopy. The MRI examination was performed at the same time to evaluate graft remodeling. The shape, tension, and degree of vascularization of grafts were observed under arthroscopy. The grafts were harvested and observed by HE staining.

Results

The invertal between ACL reconstruction and the second-look arthroscopy was (23.57±3.23) months in isokinetic group and (23.22±3.56) months in control group, showing no significant difference between the two groups ( P>0.05). At the second-look arthroscopy, the IKDC score was 90.45±4.73 in isokinetic group and 89.32±4.54 in control group, showing significant differences when compared with preoperative scores in the two groups ( P<0.05). But there was no significant difference between the two groups ( t=0.868， P=0.404). At 3 months after operation, there was no significant difference in the PT of knee extension and flexion between the two groups ( P>0.05). At 6 months, 12 months, and the second-look arthroscopy, the PT of knee extension and flexion in isokinetic group were higher than those in control group ( P<0.05). The H/Q at 6 months and 12 months were higher in isokinetic group than in control group, and the differences were significant ( P<0.05). There was no significant difference in MRI score between the two groups at 3 months, 6 months, and the second-look arthroscopy ( P>0.05). The MRI score at 12 months was significantly higher in isokinetic group than in control group ( P<0.05). At the second-look arthroscopy, there was no significant difference in the arthroscopic score between the two groups ( P>0.05), and the histological score of the isokinetic group was superior to the control group ( P<0.05).

Conclusion

On the basis of regular rehabilitation training, using the isokinetic training system to develop a suitable post-surgical isokinetic rehabilitation training program is helpful in early muscle strength recovery, early graft remodeling, and even long-term histological results after ACL reconstruction.

Isokinetic eccentric training is more effective than constant load eccentric training for quadriceps rehabilitation following anterior cruciate ligament reconstruction: a randomized controlled trial

OBJECTIVE

To compare the effects of conventional (constant load) eccentric training and isokinetic eccentric training on quadriceps muscle mass, strength and functional performance in recreational athletes following anterior cruciate ligament (ACL) reconstruction.

METHODS

Thirty recreational male athletes (25 years old) undergoing ACL reconstruction received a standard rehabilitation program. Volunteers were randomized to conventional group (CG; n = 15) or isokinetic group (IG; n = 15) to be engaged in a 6-week (2 sessions/week) quadriceps eccentric training program at the extensor chair or at the isokinetic dynamometer, respectively. Assessments of quadriceps muscle mass (through magnetic resonance imaging), strength (through isokinetic dynamometry) and self-aware functionality (through questionnaire) were performed before and after the training programs. Single leg hop test performance was assessed only at post-training evaluation.

RESULTS

IG had significantly higher improvements than CG (p < 0.05) for all muscle mass outcomes (+17-23% vs. +5-9%), as well as for isometric (+34% vs. +20%) and eccentric (+85% vs. +23%) peak torques. There was no between-group difference (p > 0.05) for concentric peak torque, Lysholm score, and single leg hop test.

CONCLUSION

Isokinetic eccentric training promotes greater responses than conventional eccentric training on quadriceps muscle mass and strength of recreational athletes following ACL reconstruction.

Quadriceps Strength and Volitional Activation After Anterior Cruciate Ligament Reconstruction: A Systematic Review and Meta-analysis

Context:

Quadriceps function is a significant contributor to knee joint health that is influenced by central and peripheral factors, especially after anterior cruciate ligament reconstruction (ACLR).

Objective:

To assess differences of unilateral quadriceps isometric strength and activation between the involved limb and contralateral limb of individuals with ACLR and healthy controls.

Data Sources:

Web of Science, SportDISCUS, PubMed, CINAHL, and the Cochrane Database were all used during the search.

Study Selection:

A total of 2024 studies were reviewed. Twenty-eight studies including individuals with a unilateral history of ACLR, isometric knee extension strength normalized to body mass, and quadriceps activation measured by central activation ratios (CARs) through a superimposed burst technique were identified for meta-analysis. The methodological quality of relevant articles was assessed using a modified Downs and Black scale. Results of methodological quality assessment ranged from low to high quality (low, n = 10; moderate, n = 8; high, n = 10).

Study Design:

Meta-analysis.

Level of Evidence:

Level 2.

Data Extraction:

Means, standard deviations, and sample sizes were extracted from articles, and magnitude of between-limb and between-group differences were evaluated using a random-effects model meta-analysis approach to calculate combined pooled effect sizes (ESs) and 95% CIs. ESs were classified as weak (d < 0.19), small (d = 0.20-0.49), moderate (d = 0.50-0.79), or large (d > 0.80).

Results:

The involved limb of individuals with ACLR displayed lower knee extension strength compared with the contralateral limb (ES, –0.78; lower bound [LB], –0.99; upper bound [UB], –0.58) and healthy controls (ES, –0.76; LB, –0.98; UB, –0.53). The involved limb displayed a lower CAR compared with healthy controls (ES, –0.84; LB, –1.18; UB, –0.50) but not compared with the contralateral limb (ES, –0.15; LB, –0.37; UB, 0.07). The ACLR contralateral limb displayed a lower CAR (ES, –0.73; LB, –1.39; UB, –0.07) compared with healthy control limbs but similar knee extension strength (ES, –0.24; LB, –0.68; UB, –0.19).

Conclusion:

Individuals with ACLR have bilateral CAR deficits and involved limb strength deficits that persist years after surgery. Deficits in quadriceps function may have meaningful implications for patient-reported and objective outcomes, risk of reinjury, and long-term joint health after ACLR.

Knee Extensors Muscle Plasticity Over a 5-Years Rehabilitation Process After Open Knee Surgery

We investigated molecular and cellular parameters which set metabolic and mechanical functioning of knee extensor muscles in the operated and contralateral control leg of 9 patients with a chronically insufficient anterior cruciate ligament (ACL; 26.6 ± 8.3 years, 8 males, 1 female) after open reconstructive surgery (week 0), after ambulant physiotherapy under cast immobilization (week 9), succeeding rehabilitation training (up to week 26), and subsequent voluntary physical activity (week 260). Clinical indices of knee function in the operated leg were improved at 52 weeks and remained at a comparable level at week 260. CSA of the quadriceps (-18%), MCSA of muscle fibers (-24%), and capillary-to-fiber ratio (-24%) in m. vastus lateralis from the ACL insufficient leg were lower at week 0 than reference values in the contralateral leg at week 260. Slow type fiber percentage (-35%) and mitochondrial volume density (-39%) were reduced in m. vastus lateralis from the operated leg at weeks 9 and 26. Composition alterations in the operated leg exceeded those in the contralateral leg and, with the exception of the volume density of subsarcolemmal mitochondria, returned to the reference levels at week 260. Leg-specific deterioration of metabolic characteristics in the vasti from the operated leg was reflected by the down-regulation of mitochondrial respiration complex I-III markers (-41-57%) at week 9. After rehabilitation training at week 26, the specific Y397 phosphorylation of focal adhesion kinase (FAK), which is a proxy for mechano-regulation, was elevated by 71% in the operated leg but not in the contralateral leg, which had performed strengthening type exercise during ambulant physiotherapy. Total FAK protein and Y397 phosphorylation levels were lowered in both legs at week 26 resulting in positive correlations with mitochondrial volume densities and mitochondrial protein levels. The findings emphasize that a loss of mechanical and metabolic characteristics in knee extensor muscle remains detectable years after untreated ACL rupture, which may be aggravated in the post-operative phase by the deterioration of slow-oxidative characteristics after reconstruction due to insufficient load-bearing muscle activity. The reestablishment of muscle composition subsequent to years of voluntary physical activity reinforces that slow-to-fast fiber transformation is reversible in humans.

Progressive Changes in Walking Kinematics and Kinetics After Anterior Cruciate Ligament Injury and Reconstruction: A Review and Meta-Analysis

CONTEXT

  Anterior cruciate ligament (ACL) injury and ACL reconstruction (ACLR) result in persistent alterations in lower extremity movement patterns. The progression of lower extremity biomechanics from the time of injury has not been described.

OBJECTIVE

  To compare the 3-dimensional (3D) lower extremity kinematics and kinetics of walking among individuals with ACL deficiency (ACLD), individuals with ACLR, and healthy control participants from 3 to 64 months after ACLR.

DATA SOURCES

  We searched PubMed and Web of Science from 1970 through 2013.

STUDY SELECTION AND DATA EXTRACTION

  We selected only articles that provided peak kinematic and kinetic values during walking in individuals with ACLD or ACLR and comparison with a healthy control group or the contralateral uninjured limb.

DATA SYNTHESIS

  A total of 27 of 511 identified studies were included. Weighted means, pooled standard deviations, and 95% confidence intervals were calculated for the healthy control, ACLD, and ACLR groups at each reported time since surgery. The magnitude of between-groups (ACLR versus ACLD, control, or contralateral limb) differences at each time point was evaluated using Cohen d effect sizes and associated 95% confidence intervals. Peak knee-flexion angle (Cohen d = -0.41) and external knee-extensor moment (Cohen d = -0.68) were smaller in the ACLD than in the healthy control group. Peak knee-flexion angle (Cohen d range = -0.78 to -1.23) and external knee-extensor moment (Cohen d range = -1.39 to -2.16) were smaller in the ACLR group from 10 to 40 months after ACLR. Reductions in external knee-adduction moment (Cohen d range = -0.50 to -1.23) were present from 9 to 42 months after ACLR.

CONCLUSIONS

  Reductions in peak knee-flexion angle, external knee-flexion moment, and external knee-adduction moment were present in the ACLD and ACLR groups. This movement profile during the loading phase of gait has been linked to knee-cartilage degeneration and may contribute to the development of osteoarthritis after ACLR.

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.

Hamstring Strength Asymmetry at 3 Years After Anterior Cruciate Ligament Reconstruction Alters Knee Mechanics During Gait and Jogging

BACKGROUND

Anterior cruciate ligament reconstruction (ACLR) using a hamstring tendon autograft often results in hamstring muscle strength asymmetry. However, the effect of hamstring muscle strength asymmetry on knee mechanics has not been reported.

HYPOTHESIS

Participants with hamstring strength asymmetry would demonstrate altered involved limb knee mechanics during walking and jogging compared with those with more symmetric hamstring strength at least 2 years after ACLR with a hamstring tendon autograft.

STUDY DESIGN

Controlled laboratory study.

METHODS

There were a total of 45 participants at least 2 years after ACLR (22 male, 23 female; mean time after ACLR, 34.6 months). A limb symmetry index (LSI) was calculated for isometric hamstring strength to subdivide the sample into symmetric hamstring (SH) (LSI ≥90%; n = 18) and asymmetric hamstring (AH) (LSI <85%; n = 18) groups. Involved knee kinematic and kinetic data were collected using 3-dimensional motion analysis during gait and jogging. Peak sagittal-, frontal-, and transverse-plane knee angles and sagittal-plane knee moments and knee powers were calculated. Independent-samples t tests and analyses of covariance were used to compare involved knee kinematic and kinetic variables between the groups.

RESULTS

There were no differences in sagittal- and frontal-plane knee angles between the groups ( P > .05 for all). The AH group demonstrated decreased tibial internal rotation during weight acceptance during gait ( P = .01) and increased tibial external rotation during jogging at initial contact ( P = .03) and during weight acceptance ( P = .02) compared with the SH group. In addition, the AH group demonstrated decreased peak negative knee power during midstance ( P = .01) during gait compared with the SH group, after controlling for gait speed, which differed between groups.

CONCLUSION

Participants with hamstring strength asymmetry showed altered involved knee mechanics in the sagittal plane during gait and in the transverse plane during gait and jogging compared with those with more symmetric hamstring strength.

CLINICAL RELEVANCE

Hamstring strength asymmetry is common at 3 years after ACLR with a hamstring tendon autograft and affects involved knee mechanics during gait and jogging. Additional research is warranted to further investigate the longitudinal effect of these alterations on knee function and joint health after ACLR.

Sagittal plane kinematics predict kinetics during walking gait in individuals with anterior cruciate ligament reconstruction

BACKGROUND

Alterations in mechanical loading following anterior cruciate ligament reconstruction may lead to the development of knee osteoarthritis. Feedback that cues a change in knee kinematics during walking gait may influence mechanical loading, yet it remains unknown if knee kinematics predict kinetics during walking gait. Our aim was to determine if sagittal plane knee kinematics predict kinetics during walking gait in anterior cruciate ligament reconstructed individuals.

METHODS

Forty-one individuals with a history of primary, unilateral anterior cruciate ligament reconstruction completed a motion capture walking gait analysis. Hierarchical linear regression analyses were used in order to determine the amount of variance in the kinetic variables of interest (peak vertical ground reaction force, instantaneous and linear vertical ground reaction force loading rate) that was individually predicted by the kinematic variables of interest (knee flexion angle at heelstrike, peak knee flexion angle, and knee flexion excursion).

FINDINGS

Knee flexion excursion of the injured limb significantly predicted 11% of the variance in peak vGRF of the injured limb after accounting for gait speed and peak knee flexion angle (ΔR²=0.11, P=0.004). After accounting for gait speed and knee flexion angle at heelstrike, knee flexion excursion significantly predicted 16% of the variance in the injured limb peak vertical ground reaction force (ΔR²=0.16, P=0.001). No kinematic variable predicted vertical ground reaction force loading rate.

INTERPRETATION

Altering knee flexion excursion may be useful as a future therapeutic target for modifying peak vertical ground reaction force during walking gait following anterior cruciate ligament reconstruction.

The Utility of Limb Symmetry Indices in Return-to-Sport Assessment in Patients With Bilateral Anterior Cruciate Ligament Reconstruction

BACKGROUND

The incidence of contralateral anterior cruciate ligament (ACL) injury after ACL reconstruction (ACLR) is high. Often, return-to-sport (RTS) tests of strength and functional hopping rely on limb symmetry indices (LSIs) to identify deficits, although the utility of these measures in athletes with bilateral ACL injuries is unknown.

PURPOSE/HYPOTHESIS

The aim of this study was to investigate if LSIs used as RTS criteria in female patients after unilateral ACLR were appropriate for female patients with bilateral ACL involvement. The hypothesis tested was that asymmetries with traditional LSI measures would be present in a population after unilateral ACLR but would not be present in a population with bilateral ACLR due to the lack of a healthy internal control limb.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

A total of 45 female subjects were classified into 3 groups: after second (contralateral) ACLR (ACLR-B; n = 15); after primary unilateral ACLR (ACLR-U; n = 15); and uninjured controls (CTRL; n = 15). After being cleared for RTS, each subject completed a single-legged hop for distance (SLHD), triple hop for distance (THD), and triple-crossover hop for distance (CHD) test, in addition to an isometric quadriceps strength test on both limbs. Means and LSI ([involved limb/uninvolved limb] × 100) were calculated for each test. Limb symmetry deficits were defined by LSI <90%.

RESULTS

Analysis of functional hop testing revealed a side × group interaction for SLHD (P = .001), THD (P = .019), and CHD (P = .04). Side-to-side differences were found in the ACLR-U group for all hop tests (P = .001-.003) and in the ACLR-B group for SLHD (P = .002) and THD tests (P = .024). No side-to side differences were seen in the CTRL group (P > .05). A side × group interaction was found for isometric quadriceps strength (P = .006), with lower LSI seen in the ACLR-U group (81% ± 17.6%) compared with the CTRL group (102.2% ± 10.8%) and the ACLR-B group (95.6% ± 24.9%). Although no interaction was seen, side-to-side differences were noted in the THD in the ACLR-U group (P = .013) and ACLR-B group (P = .024) and in the CHD in the ACLR-U group (P = .001). Despite absence of an LSI deficit, bilateral peak quadriceps strength in the ACLR-B group was comparable to the involved limb of the ACLR-U group and less than in the CTRL group (P = .012).

CONCLUSION

Both the ACLR-U and the ACLR-B groups demonstrated side-to-side deficits during functional hop tests; however, these deficits were not identified according to the clinically accepted LSI values of ≥90%, calling into question the efficacy of current RTS criteria. At the time of RTS, only individuals in the ACLR-U group demonstrated an altered LSI in quadriceps strength. Significantly lower quadriceps strength of both limbs in the ACLR-B group was seen compared with the CTRL group, despite no LSI deficits in quadriceps strength. Current use of LSIs during strength and performance tests may not be an appropriate means of identifying residual deficits in female patients after bilateral ACLR at time of RTS. Furthermore, a better indicator of strength performance in this population may need to include a comparison of strength performance values to the normative values of healthy controls.

Validity of the twitch interpolation technique for the assessment of quadriceps neuromuscular asymmetries

This study examined the validity of the twitch interpolation technique for evaluating side-to-side asymmetries in quadriceps neuromuscular function. Fifty-six subjects with a wide range of asymmetries (19 healthy, 24 with unilateral and 13 with bilateral anterior cruciate ligament reconstruction) took part in the study. Supramaximal electrical paired stimuli were delivered to the quadriceps muscle during and immediately after a maximal voluntary contraction (MVC) of the knee extensors (twitch interpolation technique). MVC torque, voluntary activation and resting doublet-evoked torque were measured separately for the two sides, and percent side-to-side asymmetries were calculated for each parameter. MVC torque asymmetry was plotted against voluntary activation asymmetry and doublet-evoked torque asymmetry, and a multiple regression analysis was also conducted. Significant positive correlations were observed between MVC torque asymmetry and both voluntary activation asymmetry (r=0.40; p=0.002) and doublet-evoked torque asymmetry (r=0.53; p<0.001), and their relative contribution to MVC torque asymmetry was comparable (r=0.64; p<0.001). These results establish the validity of the twitch interpolation technique for the assessment of neuromuscular asymmetries. This methodology could provide useful insights into the contribution of some neural and muscular mechanisms that underlie quadriceps strength deficits.

Quadriceps Strength, Muscle Activation Failure, and Patient-Reported Function at the Time of Return to Activity in Patients Following Anterior Cruciate Ligament Reconstruction: A Cross-sectional Study

STUDY DESIGN

Cross-sectional.

OBJECTIVES

To determine if quadriceps activation failure (QAF) moderates the relationship between quadriceps strength and physical function in individuals following anterior cruciate ligament (ACL) reconstruction.

BACKGROUND

Quadriceps activation failure may impair the recovery of physical function after ACL reconstruction, given that QAF reduces strength and strength is related to physical function. Evidence of this relationship has been found in individuals with knee osteoarthritis, wherein patients with lower strength and greater QAF had lower levels of physical function.

METHODS

Participants consisted of 52 individuals who were cleared for return to activity at an average ± SD of 7.4 ± 1.2 months post-ACL reconstruction. Quadriceps activation failure was assessed using the superimposed burst technique, and quadriceps strength was assessed using concentric isokinetic contractions (Newton meters per kilogram). Physical function was quantified using a combined variable of a physical measure (single-leg hop for distance) and a self-reported function measure (International Knee Documentation Committee [IKDC] Subjective Knee Evaluation Form), calculated using a principal-component analysis. Simple correlations were then performed to determine the order in which variables were entered into the regression model to evaluate if QAF moderates the relationship between quadriceps strength and physical function.

RESULTS

The combination of quadriceps strength and the interaction of strength by QAF predicted 30% of the variance in physical function (R(2) = 0.30, P<.001; principal-component analysis, -0.61(strength) + 0.02(interaction) -1.896); however, the interaction of strength by QAF only accounted for 7% of the capabilities of the model (P = .023).

CONCLUSION

Physical function is largely influenced by the recovery of quadriceps strength and minimally attenuated by QAF. These data suggest that QAF may affect individuals post-ACL reconstruction differently, and to a lesser extent, than individuals with knee osteoarthritis. This trial was prospectively registered in a public registry (NCT01555567).

A conceptual framework for a sports knee injury performance profile (SKIPP) and return to activity criteria (RTAC)

Injuries to the knee, including intra-articular fractures, ligamentous ruptures, and meniscal and articular cartilage lesions, are commonplace within sports. Despite advancements in surgical techniques and enhanced rehabilitation, athletes returning to cutting, pivoting, and jumping sports after a knee injury are at greater risk of sustaining a second injury. The clinical utility of objective criteria presents a decision-making challenge to ensure athletes are fully rehabilitated and safe to return to sport. A system centered on specific indicators that can be used to develop a comprehensive profile to monitor rehabilitation progression and to establish return to activity criteria is recommended to clear athletes to begin a progressive and systematic approach to activities and sports. Integration of a sports knee injury performance profile with return to activity criteria can guide clinicians in facilitating an athlete's safe return to sport, prevention of subsequent injury, and life-long knee joint health.

The influence of quadriceps strength asymmetry on patient-reported function at time of return to sport after anterior cruciate ligament reconstruction

BACKGROUND

An objective assessment of quadriceps strength after anterior cruciate ligament reconstruction (ACLR) is an important clinical measure to determine readiness to return to sport (RTS). Not all clinicians are equipped with the means to objectively quantify quadriceps strength limb symmetry indices (Q-LSIs) via lower extremity isokinetic dynamometers, as recommended by previous studies.

PURPOSE/HYPOTHESIS

The purpose of this study was to determine whether the International Knee Documentation Committee 2000 Subjective Knee Form (IKDC) score at time of RTS was a predictor of quadriceps strength in a young, athletic population after ACLR. Two hypotheses were tested: (1) Individuals with higher self-reports of function would demonstrate better quadriceps strength of the involved limb than individuals with lower self-reports of function at the time of RTS, and (2) individuals with higher self-reports of function would have normal quadriceps strength limb symmetry.

STUDY DESIGN

Cohort study (diagnosis); Level of evidence, 2.

METHODS

At time of RTS, 139 subjects who had undergone ACLR completed the IKDC. In addition, an isometric quadriceps strength test (Biodex dynamometer) was performed on both lower extremities. Peak torques were calculated, as was the Q-LSI, determined by the formula (involved limb peak torque/uninvolved limb peak torque) × 100%. Participants were dichotomized based on IKDC scores: high IKDC (IKDC ≥90) and low IKDC (IKDC <90). Two-way analysis of variance was used to determine the effect of limb (involved vs uninvolved) and group (high vs low IKDC) on isometric quadriceps strength. Chi-square and logistic regression analyses were then performed to determine whether IKDC scores could predict Q-LSI.

RESULTS

At time of RTS, a significant correlation between IKDC scores and (1) peak isometric torque (r = 0.282, P < .001) and (2) Q-LSI (r = 0.357, P < .001) was observed. Individuals with IKDC scores ≥90 were 3 times (OR = 3.4; 95% CI, 1.71-6.93) more likely to demonstrate higher Q-LSI (≥90%). An IKDC score ≥94.8 predicted Q-LSI ≥90% with high sensitivity (0.813) and moderate specificity (0.493).

CONCLUSION

Participants with higher IKDC scores demonstrated an increased likelihood of presenting with greater involved limb quadriceps strength and better Q-LSI. Based on the results of this study, a patient-reported outcome measure, such as the IKDC, may be able to serve as a valuable screening tool for the identification of quadriceps strength deficits in this population; however, it should not be considered an accurate surrogate for isokinetic dynamometry. Furthermore, a score of ≥94.8 on the IKDC is likely to indicate that a patient's quadriceps strength is at an acceptable RTS level.

Effect of knee angle on quadriceps strength and activation after anterior cruciate ligament reconstruction

Quadriceps strength and activation deficits after anterior cruciate ligament (ACL) injury or surgery are typically evaluated at joint positions that are biomechanically advantageous to the quadriceps muscle. However, the effect of knee joint position and the associated changes in muscle length on strength and activation is currently unknown in this population. Here, we examined the effect of knee angle on quadriceps strength, activation, and electrically evoked torque in individuals with ACL reconstruction. Furthermore, we evaluated whether knee angle mediated the relationship between quadriceps weakness and functional performance after ACL reconstruction. Knee strength and activation were tested bilaterally at 90° and 45° of knee flexion in 11 subjects with ACL reconstruction using an interpolated triplet technique. The magnitude of electrically evoked torque at rest was used to quantify peripheral muscle contractile property changes, and the single-leg hop for distance test was used to evaluate functional performance. The results indicated that although quadriceps strength deficits were similar between knee angles, voluntary activation deficits were significantly higher in the reconstructed leg at 45° of knee flexion. On the contrary, the side-to-side evoked torque at rest ratio [i.e., (reconstructed/nonreconstructed) × 100] was significantly lower at 90° than at 45° of knee flexion. The association between quadriceps strength and functional performance was stronger at 45° of knee flexion. The results provide novel evidence that quadriceps activation is selectively affected at 45° of knee flexion and emphasize the importance of assessing quadriceps strength and activation at this position when feasible because it better captures activation deficits.

Controversies in knee rehabilitation: anterior cruciate ligament injury

Controversy in management of athletes exists after anterior cruciate ligament (ACL) injury and reconstruction. Consensus criteria for evaluating successful outcomes following ACL injury include no reinjury or recurrent giving way, no joint effusion, quadriceps strength symmetry, restored activity level and function, and returning to preinjury sports. Using these criteria, the success rates of current management strategies after ACL injury are reviewed and recommendations are provided for the counseling of athletes after ACL injury.