Quadriceps Strength Asymmetry Research Articles

Interlimb Asymmetry in Knee Extension Moment During Double-Leg Squatting Is Associated With Persistent Quadriceps Weakness After ACL Reconstruction

Background: Although double-leg squatting is less dynamic and places less demand on the quadriceps compared with landing tasks, the relationship between double-leg squatting biomechanics and persistent quadriceps weakness after anterior cruciate ligament reconstruction (ACLR) is unknown. Purpose: To clarify the relationships between asymmetries in quadriceps strength and lower limb biomechanics during double-leg squatting >1 year after ACLR. Study Design: Controlled laboratory study. Methods: A total of 26 participants (5.5 ± 3.8 years after ACLR) were enrolled. The limb symmetry index (LSI) of isokinetic quadriceps strength was used to divide participants into the high-quadriceps (HQ) group (LSI ≥90%; n = 18) and the low-quadriceps (LQ) group (LSI <90%; n = 8). The knee, hip, and ankle extension moment (relative to body weight and support moment [sum of knee, hip, and ankle moments]) and vertical ground-reaction force during double-leg squatting were analyzed using 3-dimensional motion analysis. The association of quadriceps strength and biomechanical variables was tested using 2-way analysis of variance and univariate regression analysis. Results: A significant group-by-limb interaction was found for the peak knee extension moment and the ratios of knee and hip extension moment to support moment ( P < .001, P = .015 and P < .001, respectively). The LQ group showed a significantly smaller peak knee extension moment and knee to support moment ratio but a larger hip to support moment ratio in the involved limb than in the uninvolved limb (95% CIs: knee extension moment, −0.273 to −0.088 N·m/kg; knee to support moment ratio, −10.7% to −2.2%; hip to support moment ratio, 3.2% to 8.5%). No interlimb difference was found for the HQ group. The LSI of quadriceps strength was significantly associated with the LSI of peak knee extension moment ( R 2 = 0.183), knee to support moment ratio ( R 2 = 0.256), and hip to support moment ratio ( R 2 = 0.233). The mean maximum isokinetic quadriceps strength and peak knee extension moment during squatting on the involved limb of the LQ group were 2.40 ± 0.39 and 0.90 ± 0.16 N·m/kg, respectively. Conclusion: Asymmetrical biomechanics during double-leg squatting was associated with persistent quadriceps weakness after ACLR. The LQ group had reduced knee extensor moment on the involved side during squatting despite loading at approximately half the maximum strength. Clinical Relevance: Quadriceps strengthening exercises, together with interventions to improve neuromuscular control, may reduce asymmetrical biomechanics during double-leg squatting.

Explosive Hamstrings Strength Asymmetry Persists Despite Maximal Hamstring Strength Recovery Following ACL Reconstruction Using Hamstring Tendon Autografts

Introduction Hamstrings and quadriceps strength asymmetry are common after ACL reconstruction (ACLR). Conventional assessments and rehabilitation have focused on maximal strength (peak torque) as criterion for return to sport. An increasing body of evidence have shown explosive strength or rate of torque development (RTD) might be an important indicator of recovery and function following ACLR. There is some evidence that explosive quadriceps strength does not recover at the same rate as maximal quadriceps strength.

A 2-year prospective randomized controlled trial investigating an accelerated rehabilitation pathway after double-bundle, remnant sparing anterior cruciate ligament reconstruction (ACLR)

Introduction: Anterior cruciate ligament reconstruction (ACLR) is common. Insufficient quadriceps strength and functional hop asymmetry are associated with an increased re-injury risk after ACLR upon return to sport (RTS). This study sought to investigate whether an accelerated rehabilitation pathway after ACLR with a hamstring autograft could enhance strength and functional symmetry after ACLR, without affecting graft laxity and/or re-injury.

Explosive hamstrings strength asymmetry persists despite maximal hamstring strength recovery following anterior cruciate ligament reconstruction using hamstring tendon autografts

PurposeTo investigate the differences in maximal (isometric and concentric peak torque) and explosive (rate of torque development (RTD)) hamstring and quadriceps strength symmetry between males and females during early- and late-phase rehabilitation after anterior cruciate ligament reconstruction (ACLR) using hamstring tendon (HT) autografts and to determine the interaction of time and sex on maximal and explosive strength symmetry.MethodsA total of 38 female and 51 male participants were assessed during early (3–6 months post-operative) and late (7–12 months post-operative) phases of rehabilitation following ACLR. Maximal (concentric and isometric peak torque) and explosive (isometric RTD) hamstring and quadriceps strength were assessed and presented as limb symmetry index (LSI).ResultsMaximal concentric hamstrings asymmetry (Early: 86 ± 14; Late 92 ± 13; p = 0.005) as well as maximal concentric (Early, 73 ± 15; Late 91 ± 12; p < 0.001) and explosive (Early: 82 ± 30; Late: 92 ± 25; p = 0.03) quadriceps asymmetry decreased from early to late rehabilitation. However, there were no significant changes in maximal isometric quadriceps strength and explosive isometric hamstring strength in the same time period. Females had a larger asymmetry in maximal concentric (Females: 75 ± 17; Males: 81 ± 15; p = 0.001) and explosive (Females: 81 ± 32; Males: 89 ± 25; p = 0.01) quadriceps strength than males throughout rehabilitation. There were no sex differences in maximal and explosive hamstring strength. There were no sex by time interactions for any variables.ConclusionExplosive hamstring strength asymmetry did not improve despite recovery of maximal hamstring strength during rehabilitation following ACLR with HT autografts. While sex did not influence strength recovery, females had larger maximal and explosive quadriceps strength asymmetry compared to males throughout rehabilitation following ACLR.Level of evidenceLevel III

Predictors of Quadriceps Strength Asymmetry after Anterior Cruciate Ligament Reconstruction: A Chi-Squared Automatic Interaction Detection Decision Tree Analysis.

The influence of graft type on the restoration of quadriceps strength symmetry after ACL reconstruction (ACLR) has been widely studied. However, an important consideration when evaluating quadriceps symmetry is the fact that this measure can be influenced by numerous factors beyond graft type. This study sought to determine if graft type is predictive of quadriceps strength asymmetry during the first 12 months post-ACLR taking into consideration potentially influential factors (i.e., age, sex, body mass index, time post-ACLR). We retrospectively reviewed quadriceps strength data from 434 patients (303 female patients and 131 male patients) who had previously undergone ACLR with an autograft (hamstring tendon, quadriceps tendon [QT], patellar tendon [PT]) or allograft. Chi-Squared Automatic Interaction Detection decision tree analysis was used to evaluate if graft type is predictive of quadriceps strength asymmetry during the first 12 months post-ACLR taking into consideration age, sex, body mass index, and time post-ACLR. The best predictor of quadriceps strength asymmetry was graft type. Specifically, three graft categories were identified: 1) allograft and hamstring tendon autograft, 2) PT autograft, and 3) QT autograft. The average quadriceps strength asymmetry for each of the three identified categories was 0.91, 0.87, and 0.81, respectively, and differed statistically from each other ( P < 0.001). The second-best predictor of quadriceps strength asymmetry was sex, albeit only in the PT and QT groups (with female patients having increased asymmetry). Female patients post-ACLR with a QT autograft were at highest risk for quadriceps strength asymmetry. Graft type and sex are important predictors of quadriceps strength asymmetry after ACLR. Clinicians should take these factors into consideration when designing rehabilitation protocols to restore quadriceps strength symmetry during the postoperative period.

Paper 23: The Impact of Graft Choice on Return to Sport Testing After Adolescent ACL Reconstruction

Objectives:The number of anterior cruciate ligament (ACL) injuries and reconstructions observed in the adolescent population continues to rise. While the use of quadriceps tendon autograft has increased in popularity in this population, there remains no consensus on the ideal graft for pediatric ACL reconstruction. The objective of this study was to compare three commonly used ACL graft types with respect to i) performance on return to sport assessments and ii) timing to clearance for return to sports in an adolescent population.Methods:All patients, less than or equal to 19 years of age, who underwent reconstruction for ACL tears between 2016 and 2020 at a large, urban, academic institution were identified. Graft choice was made in a shared decision-making model with patient, parents, and surgeon. Patient demographics, laterality, graft type, time from surgery to clearance, number of physical therapy (PT) visits, and presence of concomitant meniscus injuries were collected from the electronic medical record. At a minimum of 6 months postoperatively, patients completed a formal return to sport test (RTS) including isometric strength assessments, Y- balance testing, and hop testing. Treatment cohorts based on graft type were compared with respect to RTS performance and timing to clearance. Associations between patient demographics and return to sport timing and performance were also assessed. Clearance for return to sport was determined by the treating surgeon with limb symmetry index of 90% on RTS as the goal for clearance.Results:A total of 110 adolescents, 44 female (40%), with a mean age of 16.3 years (SD, 1.7; range, 10-19) met our inclusion criteria (Table 1). Average time to first RTS assessment was 280 days (9.3 months) and average time to clearance was 371 days (12.2 months) after surgery. ACL grafts included 58 (52.7%) hamstring autografts, 26 (23.6%) bone-patellar tendon-bone (BPTB) autografts, 21 (19.1%) bone quadriceps (BQT) autografts, and 5 (4.6%) iliotibial band (ITB) autografts. ITB patients were younger on average (12.5 years old) than those receiving hamstring, BPTB or BQT grafts. There were no significant differences between groups with respect to laterality, number of physical therapy visits, or rate of concurrent meniscus surgery.Patients receiving BQT grafts were more likely to be cleared within 1 year of surgery compared to hamstring graft patients (82.4% vs. 39.6%, p=0.002) and had similar rates of clearance within 1 year compared to BPTB patients (82.4% vs. 65.2%, p=0.230). Patients with BQT and BPTB grafts both demonstrated significantly better hamstring strength symmetry compared to hamstring graft patients (5.8% strength deficit compared to healthy side vs. 1.3% vs. 29.3%, p<0.001) (Table 2). There were no differences in quadriceps strength or hop test asymmetry between graft types. Multivariate regression with age, gender, and number of PT sessions included as covariates demonstrated that hamstring graft choice was associated with decreased odds of clearance at 1 year.Conclusions:In this study of 110 adolescent ACL reconstruction patients who underwent return to sport evaluations, we found no significant difference between BPTB and BQT autografts with respect to RTS performance and time to clearance. Hamstring autograft was associated with significantly worse hamstring strength asymmetry and significantly lower rates of clearance within 1 year. Concurrent meniscus surgery, age, gender, and number of PT sessions completed prior to RTS evaluation were not significantly associated with timing of clearance or performance on the RTS assessment.Table 1.Patient Demographics and Surgical CharacteristicsTable 2.Patient Demographics and Performance by 3 Common Graft Types

Association between quadriceps strength asymmetry and incidence of falls among patients with knee osteoarthritis：The SPSS-OK study

Association between quadriceps strength asymmetry and incidence of falls among patients with knee osteoarthritis：The SPSS-OK study

The associations between asymmetries in quadriceps strength and gait in individuals with unilateral transtibial amputation.

Individuals with unilateral transtibial amputations (ITTAs) are asymmetrical in quadriceps strength. It is unknown if this is associated with gait performance characteristics such as walking speed and limb symmetry. Are quadriceps strength asymmetries related to walking speed and/ or gait asymmetries in ITTAs? Knee-extensor isometric maximum voluntary torque (MVT) and rate of torque development (RTD) were measured in eight ITTAs. Gait data were captured as the ITTAs walked at self-selected habitual and fast speeds. Step length and single support time, peak knee extension moments and their impulse and peak vertical ground reaction force (vGRF) in the braking and propulsive phases of stance were extracted. Bilateral Asymmetry Index (BAI) and, for gait variables only, difference in BAI between walking speeds (ΔBAI) were calculated. Correlation analyses assessed the relationships between MVT and RTD asymmetry and (1) walking speed; (2) gait asymmetries. Associations between strength and gait BAIs generally became more apparent at faster walking speeds, and when the difference in BAI between fast and habitual walking speed was considered. BAI RTD was strongly negatively correlated with habitual and fast walking speeds (r=∼0.83). Larger BAI RTD was strongly correlated with propulsive vGRF BAI in fast walking, and larger ΔBAIs in vGRF during both the braking and propulsion phases of gait (r = 0.74-0.92). ITTAs who exhibited greater BAI MVT showed greater ΔBAI in single support time (r = 0.83). While MVT and RTD BAI appear to be associated with gait asymmetries in ITTAs, the magnitude of the asymmetry in RTD appears to be a more sensitive marker of walking speed. Based on these results, it's possible that strengthening the knee-extensors of the amputated limb to improve both MVT and RTD symmetry may benefit walking speed, and reduce asymmetrical loading in gait.

Confidence to Return to Play After ACL Reconstruction: An Evaluation of Quadriceps Strength Symmetry and Injury Mechanism in Male Athletes.

After anterior cruciate ligament reconstruction (ACLR), diminished quadriceps strength symmetry and reduced psychological readiness to return to play (RTP) increase the risk for subsequent injury. Although the relationship between quadriceps strength symmetry and psychological readiness to RTP has been reported to be influenced by injury mechanism in female athletes, it is unclear whether such a relationship exists in male athletes. Quadriceps strength symmetry would be positively associated with greater psychological readiness to RTP after ACLR, regardless of injury mechanism. Retrospective cohort. Level 3 (cohort study). Sixty male patients completed strength testing and the Injury-Psychological Readiness to Return to Sport Scale (I-PRRS) at an outpatient clinical facility as part of return to sport testing after ACLR. Linear regression analysis was used to assess the relationship between the I-PRRS and the independent variables of interest (quadriceps strength symmetry and injury mechanism). For all patients combined, no symmetry × mechanism interaction was found (P = 0.11). A significant positive relationship was found between quadriceps strength symmetry and the I-PRRS score (P < 0.001, R2 = 0.31), after adjusting for time post-ACLR and injury mechanism. Greater quadriceps strength symmetry was associated with greater psychological readiness to RTP after ACLR in male athletes. In contrast to what has been reported in female athletes, this relationship was independent of injury mechanism. Given the potential negative consequences of quadriceps strength deficits on one's confidence to RTP, the need to restore quadriceps symmetry during the postoperative period is readily apparent. Low confidence or low psychological readiness to RTP may be indicative of quadriceps strength asymmetry or poor physical function in general.

Quadriceps strength asymmetry as predictor of ankle sprain in male volleyball players.

Ankle sprain is the most common acute time-loss injury in volleyball and occurs mainly during landing from a jump. Therefore, we have evaluated the role of quadriceps strength and countermovement jump height on ankle sprain occurrence, as these intrinsic modifiable risk factors were not yet evaluated. We have also hypothesized that presence of quadriceps strength asymmetry could be a possible risk factor for ankle sprains in male volleyball players. This was a prospective cohort study. Male volleyball players (N.=99) from Slovenian national league participated in the study. Before the start of the season, all participants completed a preseason questionnaire and underwent evaluation of vertical jump performance and bilateral isokinetic strength of the quadriceps (Q) and hamstrings (H). During the subsequent season the players reported acute time loss injuries because of ankle sprain through a weekly questionnaire. We have registered 19 ankle sprains during the season. Overall ankle sprain incidence was 0.41±0.24 per 1000 h. Previous ankle sprain (Odds Ratio: 0.86; 95% CI: 0.25-2.89, P=0.802) and jump height (1.05; 95% CI: 0.94-1.19, P=0.393) were not significant risk factors, while Q strength asymmetry was a significant predictor of an ankle sprain (Odds Ratio: 0.956; 95% CI: 0.919-0.995, P=0.026). Compared with the uninjured players, the injured players had higher right concentric Q strength, higher Q strength asymmetry, and lower concentric right H-Q strength ratio (all P<0.03). Our results suggest that excessive concentric strength of the right Q, which leads to low H-Q strength ratio, and high bilateral Q strength asymmetry in favor of the right side, could be associated with increased risk of ankle sprains in male volleyball.

Young athletes after ACL reconstruction with asymmetric quadriceps strength at the time of return-to-sport clearance demonstrate drop-landing asymmetries two years later

BackgroundQuadriceps strength asymmetry at the time of return-to-sport (RTS) after anterior cruciate ligament reconstruction (ACLR) contributes to altered landing mechanics. However, the impact of RTS quadriceps strength on longitudinal alterations in landing mechanics, a risk factor for poor knee joint health over time, is not understood. The purpose of this study was to test the hypothesis that young athletes with quadriceps strength asymmetry at the time of RTS clearance after ACLR would demonstrate asymmetric landing mechanics 2 years later compared to those without quadriceps strength asymmetry. MethodsWe followed 57 young athletes (age at RTS = 17.6 ± 3.0 years; 77% females) with primary, unilateral ACLR for 2 years following RTS clearance. At RTS, we measured isometric quadriceps strength bilaterally and calculated limb-symmetry indices [LSI = (involved/uninvolved)×100%]. Using RTS quadriceps LSI, we divided participants into High-Quadriceps (HQ; LSI ≥ 90%) and Low-Quadriceps (LQ; LSI < 85%) groups. Two years later, we assessed landing mechanics during a drop-vertical jump (DVJ) task using three-dimensional motion analysis. We compared involved/uninvolved limb values and LSI between the HQ and LQ groups using Mann-Whitney U tests. ResultsThe LQ group (n = 26) demonstrated greater asymmetry (lower LSI) during landing at 2 years post-RTS for knee flexion excursion (p = 0.016) and peak vertical ground reaction force (p = 0.006) compared to the HQ group (n = 28). There were no group differences in uninvolved or involved limb values for all variables (all p > 0.093). ConclusionYoung athletes after ACLR with quadriceps strength asymmetry at the time of RTS favored the uninvolved limb during DVJ landing 2 years later. These landing asymmetries may relate to long-term knee joint health after ACLR.

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

Background: After anterior cruciate ligament (ACL) reconstruction (ACLR), biomechanical asymmetries during gait are highly prevalent, persistent, and linked to posttraumatic knee osteoarthritis. Quadriceps strength is an important clinical measure associated with preoperative gait asymmetries and postoperative function and is a primary criterion for return-to-sport clearance. Evidence relating symmetry in quadriceps strength with gait biomechanics is limited to preoperative and early rehabilitation time points before return-to-sport training. Purpose/Hypothesis: The purpose was to determine the relationship between symmetry in isometric quadriceps strength and gait biomechanics after return-to-sport training in athletes after ACLR. We hypothesized that as quadriceps strength symmetry increases, athletes will demonstrate more symmetric knee joint biomechanics, including tibiofemoral joint loading during gait. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Of 79 athletes enrolled in the ACL-SPORTS Trial, 76 were participants in this study after completing postoperative rehabilitation and 10 return-to-sport training sessions (mean ± SD, 7.1 ± 2.0 months after ACLR). All participants completed biomechanical walking gait analysis and isometric quadriceps strength assessment using an electromechanical dynamometer. Quadriceps strength was calculated using a limb symmetry index (involved limb value / uninvolved limb value × 100). The biomechanical variables of interest included peak knee flexion angle, peak knee internal extension moment, sagittal plane knee excursion at weight acceptance and midstance, quadriceps muscle force at peak knee flexion angle, and peak medial compartment contact force. Spearman rank correlation (ρ) coefficients were used to determine the relationship between limb symmetry indexes in quadriceps strength and each biomechanical variable; alpha was set to .05. Results: Of the 76 participants, 27 (35%) demonstrated asymmetries in quadriceps strength, defined by quadriceps strength symmetry <90% (n = 23) or >110% (n = 4) (range, 56.9%-131.7%). For the biomechanical variables of interest, 67% demonstrated asymmetry in peak knee flexion angle; 68% and 83% in knee excursion during weight acceptance and midstance, respectively; 74% in internal peak knee extension moment; 57% in medial compartment contact force; and 74% in quadriceps muscle force. There were no significant correlations between quadriceps strength index and limb symmetry indexes for any biomechanical variable after return-to-sport training (P > .129). Conclusion: Among those who completed return-to-sport training after ACLR, subsequent quadriceps strength symmetry was not correlated with the persistent asymmetries in gait biomechanics. After a threshold of quadriceps strength is reached, restoring strength alone may not ameliorate gait asymmetries, and current clinical interventions and return-to-sport training may not adequately target gait.

Effect of improvement in quadriceps strength asymmetry on trunk movement asymmetry after total knee arthroplasty

BackgroundPatients with knee osteoarthritis (OA) demonstrate trunk movement asymmetry during walking; this asymmetry is associated with disability and quadriceps strength asymmetry. Research questionWhat are the differences between trunk movement asymmetries before and after total knee arthroplasty (TKA) and associations between the changes in trunk movement asymmetry and quadriceps strength asymmetry? MethodsIn this prospective cohort study, 27 patients (mean age, 71.0 years; women, 85.2%) were assessed at 1 month before and 6 months after surgery. Trunk movement asymmetry (harmonic ratio) was assessed at their preferred pace using a triaxial accelerometer. The isometric quadriceps strength was evaluated using a hand-held dynamometer, and the quadriceps strength inter-limb absolute difference was calculated. Multivariate analyses were performed to compare the trunk movement asymmetries before and after surgery with covariate adjustment (gait pain, gait velocity, and non-operated-limb Kellgren and Lawrence [K&L] grade) and to investigate the association between the changes in trunk movement asymmetry and quadriceps strength inter-limb difference with covariate adjustment (age, sex, and non-operated-limb K&L grade). ResultsThe trunk movement asymmetry in the medio-lateral (mean difference, 0.61; 95% confidence interval [CI], 0.22 to 1.00) and antero-posterior (mean difference, 1.15; 95% CI, 0.48 to 1.83) directions significantly decreased postoperatively compared with the preoperative results. A decreased quadriceps strength inter-limb difference was significantly associated with a decreased medio-lateral trunk movement asymmetry (β = 0.68; 95% CI, 0.30 to 1.06). SignificanceTKA plays an important role in the improvement of trunk stability during walking in patients with knee OA. Decreasing quadriceps strength asymmetry may be a key to improving trunk movement asymmetry.

The relationship between quadriceps strength asymmetry and knee biomechanics asymmetry during walking in individuals with anterior cruciate ligament reconstruction

BackgroundLower extremity movement asymmetries may lead to re-injury and knee osteoarthritis after anterior cruciate ligament (ACL) reconstruction surgery. However, there is no consensus regarding the effect of quadriceps strength asymmetry on lower extremity movement asymmetry after ACL reconstruction. Research questionWhat is the relationship between quadriceps strength asymmetry and asymmetries in lower extremity kinematics and kinetics during walking in individuals who underwent ACL reconstruction surgery?. MethodsIsometric quadriceps strength, kinematic, and kinetic data during walking were collected from 24 men with unilateral ACL reconstruction. Knee joint angles and moments were reduced. Pearson correlation coefficients between asymmetry in selected knee biomechanics and isometric quadriceps strength asymmetry were determined. ResultsThe isometric quadriceps strength of the injured leg was significantly lower than that of the uninjured leg (P < 0.001). Knee flexion angles and knee extension moments were smaller in the injured leg than that in the uninjured leg during both loading response (P = 0.007, P = 0.047) and mid-stance phases (P = 0.005, P = 0.028). Isometric quadriceps strength asymmetry was significantly correlated with asymmetry in the peak knee flexion angle during loading response and mid-stance phases (r = −0.48, P = 0.017, r = −0.48, P = 0.017). Isometric quadriceps strength asymmetry was also significantly correlated with asymmetry in the peak knee extension moment during the mid-stance phase (r = −0.44, P = 0.033). SignificanceIndividuals with ACL reconstruction demonstrate knee movement asymmetry in the sagittal plane. Isometric quadriceps strength asymmetry is significantly correlated with asymmetry in knee flexion angles during the early stance phase and knee extension moments during the mid-stance phase. Rehabilitation programs should emphasise eccentric exercise to beneficially modify quadriceps neuromuscular control.

Bilateral Quadriceps Strength Asymmetry Is Associated With Previous Knee Injury in Military Special Tactics Operators.

Eagle, SR, Keenan, KA, Connaboy, C, Wohleber, M, Simonson, A, and Nindl, BC. Bilateral quadriceps strength asymmetry is associated with previous knee injury in military special tactics operators. J Strength Cond Res 33(1): 89-94, 2019-Bilateral strength asymmetries have been related to lower-limb injury in athletes. Given that military populations often participate in recreational sport, in addition to a physically demanding workload, bilateral strength asymmetries may be related to injury in military populations. The purpose of this study was to determine whether isokinetic strength differs between Operators with/without self-reported knee injury (KI), and to examine the odds of displaying a lower-extremity strength asymmetry based on previous KI history. Operators (n = 150) self-reported injury history and performed isokinetic knee strength testing. Cohorts were separated by those who reported/not reported KI. Mean isokinetic knee strength and odds ratios, with subjects' KI history compared with strength differences: <10, 10-20, and >20%, were calculated. Operators who reported KI demonstrated larger bilateral knee extension (KE) strength differences compared with those who did not report an injury (injured: 13.5 ± 12.9% vs. noninjured: 8.1 ± 5.9%, p = 0.01). Operators with <10 or 10-20% KE strength difference had 76-77% reduced odds of previous KI, compared to those with >20% strength difference (p < 0.05). Operators with previous KI demonstrated bilateral differences in KE strength. Those with <10 or 10-20% strength differences had reduced odds of reporting previous KI. Strength and conditioning professionals should consider unilateral, targeted exercises in reducing bilateral asymmetry to rectify more balanced strength between limbs. Targeted exercise programs may improve bilateral strength differences and limit reinjury risk.

Trunk movement asymmetry associated with pain, disability, and quadriceps strength asymmetry in individuals with knee osteoarthritis: a cross-sectional study

This study examined 1) the clinical relevance of trunk movement asymmetry, which was evaluated using a trunk-mounted inertial measurement unit (IMU), and 2) the relationship between trunk movement asymmetry and lower limb muscle strength asymmetry in individuals with knee osteoarthritis (OA). One-hundred-thirty-one participants (mean age, 74.2 years; 71.8% female; Kellgren and Lawrence [K&L] grade ≥1) underwent gait analysis at their preferred pace for IMU-based measurement of trunk movement asymmetry (harmonic ratio [HR] and improved HR). The isometric strength of quadriceps and hip abductors was evaluated using a hand-held dynamometer. Pain and disability level were evaluated using a validated self-reported questionnaire. Multiple regression analyses with covariate adjustment were performed to examine the relationship between trunk movement asymmetry (independent variable) and pain, disability level, or muscle strength asymmetry (dependent variables). Individuals with severe knee OA (K&L grade ≥3) had increased trunk movement asymmetry in the medio-lateral axis compared to those with a K&L grade of 1. Increased trunk movement asymmetry was associated with a greater knee pain and disability. The increased trunk movement asymmetry was significantly associated with an increase in the asymmetry of quadriceps strength, but not with asymmetry in the strength of hip abductor. Our findings indicate that increased medio-lateral trunk movement asymmetry may be an indicator of impairment, rather than adaptation, in individuals with knee OA. This preliminary finding warrants validation by future study. Paying close attention to medio-lateral trunk movement asymmetry may be key to our understanding of OA-related pain and disability.

Quadriceps Strength and Landing Symmetry Following ACL Reconstruction

PURPOSE: Quadriceps strength asymmetry is common following anterior cruciate ligament reconstruction (ACLR). However, quadriceps strength symmetry may not reflect symmetry in other tasks such as a landing. The purpose of this study was to 1) examine the relationship between quadriceps strength symmetry and landing symmetry and 2) to compare landing mechanics between limbs of individuals with ACLR. METHODS: Quadriceps strength and landing biomechanics were assessed in 46 individuals with primary unilateral ACL reconstruction (34 females, age=22.0±2.8 years, height=1.70±.09m, mass=71.9±16.1kg, IKDC=86.1±9.3). Participants completed 3 drop jump landings from a 30cm height located at a distance of 50% of their height onto 2 force plates. Quadriceps strength was assessed via isometric (peak and rate of torque development (RTD)) and isokinetic knee extension at 60°, 180°, and 240°/second. Limb symmetry index (LSI) was calculated as the ratio of the involved divided by the uninvolved limb for strength and landing biomechanics (knee flexion angle (KFA) (at ground contact, peak, and excursion), peak external knee flexion moment (KFM), and vertical ground reaction force (GRF)). Pearson correlation was used to assess the relationship between quadriceps LSIs and KFM and GRF LSIs. Spearman rho was used to examine the relationship between quadriceps LSIs and KFA LSIs. Paired samples t-tests were used to compare dependent variables between limbs (α=0.05). RESULTS: Isometric strength LSI (r=0.30, p=0.05) and RTD LSI (r=0.37, p=0.01) were associated with KFM LSI. Isometric strength LSI (rho=0.34, p=0.02) and isokinetic strength LSI at 60° (rho=0.40, p=0.01) and 180° (rho=0.31, p=0.05) were associated with knee flexion excursion LSI. Isokinetic strength at 180° (r=0.39, p=0.01) was associated with GRF LSI. Uninvolved limbs had greater GRF (2.48±0.77 vs. 2.23±0.69 BW, p=0.034) and KFM (0.17±0.04 vs. 0.14±0.04 %BW*height, p<0.001) compared to involved limbs. CONCLUSIONS: ACLR limbs had smaller GRF and KFM compared to uninvolved limbs. This may indicate a compensatory strategy to underload the involved limb during landing. The weak correlations between quadriceps strength LSI and landing LSI may indicate that other factors such as impaired neuromuscular control or fear of re-injury influence landing symmetry.

Quadriceps weakness preferentially predicts detrimental gait compensations among common impairments after total knee arthroplasty.

Patients with total knee arthroplasty (TKA) have large deficits in physical performance in comparison to their healthy age-matched peers. Limb asymmetry stemming from less relative load borne by the surgical limb during daily mobility is associated with diminished performance and worsens with greater mobility demands. How common targets of postoperative care, such as muscle weakness, lower limb extension power, residual knee pain, and poor balance confidence can influence asymmetrical limb loading remains unclear. Forty-six patients with unilateral TKA underwent testing of impairments and motion analysis during 10° decline walking at 3 and 6 months postoperatively. At 3 months, only quadriceps femoris strength asymmetry was found to be significantly related to both total support moment (MT ) (β = 0.431; p < 0.001) and knee extensor moment (MK ) (β = 0.493; p < 0.001) asymmetry. Again at 6 months, only quadriceps strength asymmetry was related to MT (β = 0.432; p < 0.001) and MK (β = 0.534; p < 0.001) asymmetry. Quadriceps strength significantly improved over time in both limbs, however, deficits between limbs remained. Persistent quadriceps weakness is a key factor associated with walking compensation patterns that are limiting the capacity for greater physical performance of patients with TKA. The pronounced asymmetry in limb and knee loading at 3 months remains unchanged until at least 6 months after surgery, and its association with quadriceps strength asymmetry does not substantially change over time. While other factors may also prompt gait compensations, emphasis on improved quadriceps strength should be a focus of efforts to resolve gait compensations and enhance physical performance outcomes. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2355-2363, 2018.

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

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

Quadriceps strength asymmetry predicts loading asymmetry during sit-to-stand task in patients with unilateral total knee arthroplasty.

This study aimed to examine interlimb differences in muscle strength and sit-to-stand (STS) kinetics in persons who underwent unilateral total knee arthroplasty (TKA) and to determine whether knee pain, quadriceps or hip abductor weakness contributes to altered STS performance. It was hypothesized that the operated limb would have weaker muscles, lower mechanical loading and that operated knee pain and muscle strength symmetry would predict loading symmetry between limbs during STS. One hundred and forty-two patients, 6 or 12months post-unilateral TKA, underwent 3D motion analysis (VICON) of the STS task and isometric strength testing of the quadriceps and hip abductors. Knee pain was also quantified using a question from the Knee Outcome Survey-Activities of Daily Living Scale. The operated limb had weaker quadriceps (P<0.001), lower hip (P=0.004) and knee extension moments (P<0.001), and lower vertical ground reaction forces (P<0.001). Operated knee pain and quadriceps strength symmetry were related to symmetry in knee extension moment (P<0.04), and vertical ground reaction forces (P<0.02) 6months after surgery, while quadriceps strength symmetry was related to symmetry in vertical ground reaction forces (P=0.03), 1year after surgery. Patients with unilateral TKA unload the operated limb and shift the mechanical load to the joints of the contralateral limb even 1year after surgery. Knee pain and quadriceps strength asymmetry may play a role in the asymmetrical loading during STS post-TKA. Clinicians should consider addressing these modifiable impairments to resolve the loading asymmetry. III.