Do Muscle Strength Deficits of the Uninvolved Hip and Knee Exist in Young Athletes Before Anterior Cruciate Ligament Reconstruction?

Strength of the Uninvolved Limb Following Return to Activity After ACL Injury: Implications for Symmetry as a Marker of Sufficient Strength

Background

Muscular strength deficits are common after ACL injury. While the Limb Symmetry Index (LSI), using the uninvolved limb as a reference, is widely used, negative strength adaptations may affect both limbs post-injury. It is uncertain how the strength of the uninvolved limb in those with an ACL injury compares to uninjured individuals, making it unclear whether it is appropriate as a benchmark for determining sufficient strength.

Purpose

To compare the strength of key lower extremity muscles of the uninvolved limb in those with history of ACL injury (ACL-I) to the dominant limb in individuals with no history of ACL injury (control).

Study Design

Cross-sectional study. Methods: A total of 5,727 military cadets were examined, with 82 females and 126 males in the ACL-I group and 2,146 females and 3,373 males in the control group. Maximum isometric strength was assessed for six muscle groups measured with a hand-held dynamometer. Separate two-way ANOVAs with limb and sex were performed for each muscle group.

Results

Significant main effects for limb were observed with the uninvolved limb in the ACL-I group displaying greater strength compared to the dominant limb in the control group for the quadriceps, hamstrings, and gluteus medius, but effect sizes were small (Cohen's d <0.25). Significant main effects for sex were observed with greater male muscular strength in all six muscle groups with small to large effect sizes (Cohen's d 0.49-1.46). No limb-by-sex interactions were observed.

Conclusions

There was no evidence of reduced strength in the uninvolved limb in those with a history of ACL injury compared to the dominant limb in those with no prior ACL injury. This finding suggests that, after clearance to return to activities, the uninvolved limb can be used as a standard for comparison of sufficient strength, including when using the LSI. Level of Evidence: Level 3.

No sign of weakness: a systematic review and meta-analysis of hip and calf muscle strength after anterior cruciate ligament injury

OBJECTIVE

We aimed to determine hip and lower-leg muscle strength in people after ACL injury compared with an uninjured control group (between people) and the uninjured contralateral limb (between limbs).

DESIGN

Systematic review with meta-analysis.

DATA SOURCES

MEDLINE, EMBASE, CINAHL, Scopus, Cochrane CENTRAL and SportDiscus to 28 February 2023.

ELIGIBILITY CRITERIA

Primary ACL injury with mean age 18-40 years at time of injury. Studies had to measure hip and/or lower-leg muscle strength quantitatively (eg, dynamometer) and report muscle strength for the ACL-injured limb compared with: (i) an uninjured control group and/or (ii) the uninjured contralateral limb. Risk of bias was assessed according to Cochrane Collaboration domains.

RESULTS

Twenty-eight studies were included (n=23 measured strength ≤12 months post-ACL reconstruction). Most examined hip abduction (16 studies), hip extension (12 studies) and hip external rotation (7 studies) strength. We found no meaningful difference in muscle strength between people or between limbs for hip abduction, extension, internal rotation, flexion or ankle plantarflexion, dorsiflexion (estimates ranged from -9% to +9% of comparator). The only non-zero differences identified were in hip adduction (24% stronger on ACL limb (95% CI 8% to 42%)) and hip external rotation strength (12% deficit on ACL limb (95% CI 6% to 18%)) compared with uninjured controls at follow-ups >12 months, however both results stemmed from only two studies. Certainty of evidence was very low for all outcomes and comparisons, and drawn primarily from the first year post-ACL reconstruction.

CONCLUSION

Our results do not show widespread or substantial muscle weakness of the hip and lower-leg muscles after ACL injury, contrasting deficits of 10%-20% commonly reported for knee extensors and flexors. As it is unclear if deficits in hip and lower-leg muscle strength resolve with appropriate rehabilitation or no postinjury or postoperative weakness occurs, individualised assessment should guide training of hip and lower-leg strength following ACL injury.

PROSPERO REGISTRATION NUMBER

CRD42020216793.

Beware of the "Moving Target" - Uninvolved Limb Strength Increases to Exceed Preoperative Values During Rehabilitation After ACL Reconstruction in Male Professional and Recreational Athletes

OBJECTIVE: To describe the changes in quadriceps and hamstrings muscle strength in the uninvolved limb of male professional and recreational athletes during rehabilitation after anterior cruciate ligament reconstruction (ACLR) and compare to preoperative strength values. DESIGN: Prospective longitudinal study. METHODS: During rehabilitation, 665 participants who underwent unilateral ACLR performed a strength test preoperatively and every 6 weeks after surgery for up to 9 months. Isokinetic quadriceps and hamstrings strength of the uninvolved limb were measured at an angular velocity of 60°/s and normalized to body weight (N·m/kg). RESULTS: Quadriceps and hamstrings strength of the uninvolved limb gradually increased during rehabilitation until 6 months post-ACLR, and plateaued thereafter. Postoperative quadriceps' strength significantly exceeded preoperative values by 3 months for professional (2.99 N·m/kg; 95% confidence interval [CI]: 2.93, 3.04; P = .007) and by 6 months for recreational athletes (2.77 N·m/kg; 95% CI: 2.71, 2.83; P<.001), and hamstrings exceeded presurgery levels by 4.5 months (1.71 N·m/kg; 95% CI: 1.67, 1.74; P<.001 and 1.43 N·m/kg; 95% CI: 1.40, 1.46; P = .002, professional and recreational athletes respectively). CONCLUSION: In male professional and recreational athletes, uninvolved limb quadriceps and hamstrings strength gradually improved after ACLR, until 6 months after surgery. The uninvolved limb's strength may present as a "moving target" that requires consistent monitoring during rehabilitation. J Orthop Sports Phys Ther 2024;54(4):1-9. Epub 14 December 2023. doi:10.2519/jospt.2023.11961.

Bilateral impairments of quadriceps neuromuscular function occur early after anterior cruciate ligament injury

The study aimed to investigate the impairments in quadriceps neuromuscular function, including strength, rate of torque development (RTD) and activation failure (QAF) early after an ACL injury. A cross-sectional study was conducted. Thirty physically active patients with a primary ACL injury within three months, aged 18 to 40 years old, and who were scheduled for ACL reconstruction were included. Thirty matched healthy controls were also recruited. All the outcomes were measured on an isokinetic dynamometer with knee flexion at 45°. Quadriceps strength was measured by maximal voluntary isometric contractions (MVIC). Early (RTD0-50) and late (RTD100-200) phases of RTD were retrieved from the MVIC test from 0 to 50 ms and 100-200 ms, respectively. QAF was quantified by the central activation ratio (CAR) measured by superimposed burst technique. The results of Mann-Whitney U test showed that compared with the healthy limbs, the injured limbs of the ACL group showed lower quadriceps strength (P < 0.001), RTD0-50 (P < 0.001) and RTD100-200 (P < 0.001); the uninjured limbs showed lower quadriceps strength (P = 0.009), RTD0-50 (P = 0.006) as well as greater QAF (P = 0.010). To conclude, bilateral quadriceps suffered from neuromuscular impairments early after an ACL injury.

Reconsideration of Return-to-Sport Decision-Making After Pediatric ACL Injury: A Scoping Review

CONTEXT

Up to 90% of pediatric athletes return to sport (RTS) after anterior cruciate ligament reconstruction (ACL-R); however, <50% RTS at the same level and second ACL injury rates are up to 32%.

OBJECTIVES

(1) Determine which physical and patient-reported outcome measures guide clinical decision-making on RTS in pediatric athletes after ACL-R and (2) present a framework with insights from cognitive and neurophysiological domains to enhance rehabilitation outcomes.

DATA SOURCES

PubMed, CINAHL, Embrase, and Cochrane library databases and gray literature.

STUDY SELECTION

Data on pediatric (<18 years) ACL-R patients, RTS, tests, and decision-making were reported in 1214 studies. Two authors independently reviewed titles and abstract, excluding 962 studies. Gray literature and cross-reference checking resulted in 7 extra studies for full-text screening of 259 studies. Final data extraction was from 63 eligible studies.

STUDY DESIGN

Scoping review.

LEVEL OF EVIDENCE

Level 4.

DATA EXTRACTION

Details on study population, aims, methodology, intervention, outcome measures, and important results were collected in a data chart.

RESULTS

Studies included 4456 patients (mean age, 14 years). Quadriceps and hamstring strength (n = 25), knee ligament arthrometer (n = 24), and hop tests (n = 22) were the most-reported physical outcome measures guiding RTS in <30% of studies with cutoff scores of limb symmetry index (LSI) ≥85% or arthrometer difference <3 mm. There were 19 different patient-reported outcome measures, most often reporting the International Knee Documentation Committee (IKDC) (n = 24), Lysholm (n = 23), and Tegner (n = 15) scales. Only for the IKDC was a cutoff value of 85% reported.

CONCLUSION

RTS clearance in pediatric ACL-R patients is not based on clear criteria. If RTS tests were performed, outcomes did not influence time of RTS. Postoperative LSI thresholds likely overestimate knee function since biomechanics are impaired despite achieving RTS criteria. RTS should be considered a continuum, and biomechanical parameters and contextual rehab should be pursued with attention to the individual, task, and environment. There is a need for psychological monitoring of the ACL-R pediatric population.

Hip rotation muscle strength is implicated in the progression of early post-traumatic osteoarthritis: A longitudinal evaluation up to 5 years following ACL reconstruction

INTRODUCTION

Following ACL reconstruction (ACLR), deficits in hip muscle strength and relationships to future outcomes are unknown.

METHODS

111 participants one year after ACLR, completed hip external rotation (ER) and internal rotation (IR) strength assessment. At 1 (n = 111) and 5 (n = 74) years post-ACLR, participants completed a battery of functional, symptomatic (Knee Osteoarthritis Outcome Score (KOOS)) and structural assessments (radiography, magnetic resonance imaging (MRI)). Cartilage health of the patellofemoral and tibiofemoral compartments was assessed with the semiquantitative MRI Osteoarthritis Knee Score. Hip rotation strength was compared between-limbs, and relationships between hip strength at 1 year and functional, symptomatic and cartilage outcomes at 1 and 5 years were investigated with regression models.

RESULTS

The index (ACLR) limb had weaker hip ER (but not IR) strength compared to the contralateral side (standardised mean difference ER = -0.33 (95%CI -0.60, -0.07; IR = -0.11 (95%CI -0.37, 0.15). Greater hip ER and IR strength was associated with superior function at 1 and 5 years, and better KOOS-Patellofemoral symptoms at 5 years. Greater hip ER strength was associated with lower odds of worsening tibiofemoral cartilage lesions at 5 years (odds ratio 0.01, 95%CI 0.00, 0.41).

CONCLUSION

Hip rotation strength may play a role in worsening function, symptoms and cartilage health after ACLR.

Hip Strength Recovery After Anterior Cruciate Ligament Reconstruction

Background

Return-to-play (RTP) assessment after anterior cruciate ligament reconstruction (ACLR) rarely includes hip strength.

Hypothesis

It was hypothesized that (1) patients after ACLR will have weaker hip abduction (AB) and adduction (AD) strength compared with the contralateral limb, with larger deficits in women, (2) there will be a correlation between hip and thigh strength ratios and patient-reported outcomes (PROs), and (3) hip AB and AD strength will improve over time.

Study Design

Descriptive laboratory study.

Methods

Included were 140 patients (74 male, 66 female; mean age, 24.16 ± 10.82 years) who underwent RTP assessment at 6.1 ± 1.6 months after ACLR; 86 patients underwent a second assessment at 8.2 ± 2.2 months. Hip AB/AD and knee extension/flexion isometric strength were measured and normalized to body mass, and PRO scores were collected. Strength ratios (hip vs thigh), limb differences (injured vs uninjured), sex-based differences, and relationships between strength ratios and PROs were determined.

Results

Hip AB strength was weaker on the ACLR limb (ACLR vs contralateral: 1.85 ± 0.49 vs 1.89 ± 0.48 N·m/kg; P < .001) and hip AD torque was stronger (ACLR vs contralateral: 1.80 ± 0.51 vs 1.76 ± 0.52 N·m/kg; P = .004), with no sex-by-limb interaction found. Lower hip-to-thigh strength ratios of the ACLR limb were correlated with higher PRO scores (r = -0.17 to -0.25). Over time, hip AB strength increased in the ACLR limb more than in the contralateral limb (P = .01); however, the ACLR limb remained weaker in hip AB at visit 2 (ACLR vs contralateral: 1.88 ± 0.46 vs 1.91 ± 0.45 N·m/kg; P = .04). In both limbs, hip AD strength was greater at visit 2 than visit 1 (ACLR: 1.82 ± 0.48 vs 1.70 ± 0.48 N·m/kg; contralateral: 1.76 ± 0.47 vs 1.67 ± 0.47 N·m/kg; P < .01 for both).

Conclusion

The ACLR limb had weaker hip AB and stronger AD compared with the contralateral limb at initial assessment. Hip muscle strength recovery was not influenced by sex. Hip strength and symmetry improved over the course of rehabilitation. Although strength differences across limbs were minor, the clinical importance of these differences is still unknown.

Clinical Relevance

The evidence provided highlights the need to integrate hip strength into RTP assessments to identify hip strength deficits that may increase reinjury or lead to poor long-term outcomes.

Knee Isokinetic Profiles and Reference Values of Professional Female Soccer Players

Few studies have previously evaluated isokinetic parameters in female soccer players in comparison to those in males. The aim of this study was to describe normative quadriceps (Q) and hamstring (H) muscle strength values in professional female soccer players and to examine differences between dominant leg (DL) and nondominant leg (NDL). A standardized test protocol of concentric knee extension and flexion test protocol was conducted using the dynamometer isokinetic system (IsoMEd 2000). All the participants were healthy female professional soccer players from Spanish first and second division teams. Players were assessed for peak torque (PT) and maximum work (MW) values at 60°/s, 180°/s, and 240°/s. The mean difference was 7.17 (p-value = 0.0036), 4.4 (p-value = 0.0386), and 4.25 Nm (p-value = 0.0241) at speed 60°, 180°, and 240°/s, respectively. No statistically significant differences were detected for H-Q values between DL and NDL. This difference was 6.44 (p-value = 0.0449), and 5.87 J (p-value = 0.0266) at speed 60°, and 180°/s. The present study can be a tool that health professionals working with female professional soccer players in their care can use to assess and monitor a particular player.

Neuromuscular Control During Stair Descent and Artificial Tibial Translation After Acute ACL Rupture

Background:

Anterior cruciate ligament (ACL) rupture has direct effect on passive and active knee stability and, specifically, stretch-reflex excitability.

Purpose/Hypothesis:

The purpose of this study was to investigate neuromuscular activity in patients with an acute ACL deficit (ACL-D group) compared with a matched control group with an intact ACL (ACL-I group) during stair descent and artificially induced anterior tibial translation. It was hypothesized that neuromuscular control would be impaired in the ACL-D group.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

Surface electromyographic (EMG) activity of the vastus medialis (VM), vastus lateralis (VL), biceps femoris (BF), and semitendinosus (ST) muscles was recorded bilaterally in 15 patients with ACL-D (mean, 13.8 days [range, 7-21 days] since injury) and 15 controls with ACL-I during stair descent and artificially induced anterior tibial translation. The movements of stair descent were divided into preactivity, weight acceptance, and push-off phases. Reflex activity during anterior tibial translation was split into preactivity and short, medium, and late latency responses. Walking on a treadmill was used for submaximal EMG normalization. Kruskal-Wallis test and post hoc analyses with Dunn-Bonferroni correction were used to compare normalized root mean square values for each muscle, limb, movement, and reflex phase between the ACL-D and ACL-I groups.

Results:

During the preactivity phase of stair descent, the hamstrings of the involved leg of the ACL-D group showed 33% to 51% less activity compared with the matched leg and contralateral leg of the ACL-I group (P < .05). During the weight acceptance and push-off phases, the VL revealed a significant reduction (approximately 40%) in the involved leg of the ACL-D group compared with the ACL-I group. At short latency, the BF and ST of the involved leg of the ACL-D group showed a significant increase in EMG activity compared with the uninvolved leg of the ACL-I group, by a factor of 2.2 to 4.6.

Conclusion:

In the acute phase after an ACL rupture, neuromuscular alterations were found mainly in the hamstrings of both limbs during stair descent and reflex activity. The potential role of prehabilitation needs to be further studied.

Twelve-Week Quadriceps Strength as A Predictor of Quadriceps Strength At Time Of Return To Sport Testing Following Bone-Patellar Tendon-Bone Autograft Anterior Cruciate Ligament Reconstruction

BACKGROUND

Restoration of quadriceps strength following anterior cruciate ligament reconstruction (ACL-R) continues to challenge both patients and clinicians. Failure to adequately restore quadriceps strength has been linked to decreased patients' self-reported outcomes and an increased risk for re-injury. Early identification of quadriceps strength deficits may assist in tailoring early interventions to better address impairments.

PURPOSE

The purpose of this study was to assess the relationship between early (12 weeks following ACL-R) isokinetic peak torque and isokinetic peak torque at time of return to sport (RTS) testing.

STUDY DESIGN

Cohort Study.

METHODS

A total of 120 participants (males = 55; females =65) were enrolled in the study (age = 16.1±1.4 yrs; height = 1.72±10.5 m; mass = 70.7±16.3 kg). All participants were level 1 or 2 cutting and pivoting sport athletes who underwent a primary bone-patellar tendon-bone autograft ACL-R. Participants were tested at two time points: 12 weeks following surgery and again at time of RTS testing. A linear regression model was carried out to investigate the relationship between age, sex, and isokinetic peak torque at 12 weeks following ACL-R and isokinetic peak torque at time of RTS testing.

RESULTS

When 12-week isokinetic peak torque was entered first for the hierarchy regression analysis, this factor was predictive of the peak torque at the time of RTS testing, F(1, 118) = 105.6, p < 0.001, R 2 = 0.472, indicating that the 12-week quadriceps strength accounted for 47% of the variance in the quadriceps strength at the time of RTS testing. When age and sex were added in the regression analysis, both factors only added 0.8% of variance for the quadriceps strength at the time of RTS testing.

CONCLUSION

Isokinetic peak torque at 12 weeks following surgery was shown to be a significantly strong predictor (47%) for isokinetic quadriceps strength recovery at time of RTS. This finding underscores the importance of early restoration of quadriceps strength and that while non-modifiable factors such as sex and age are important, early restoration of quadriceps strength most strongly influences late stage quadriceps strength.

LEVEL OF EVIDENCE

3.

Limb dominance influences energy absorption contribution (EAC) during landing after anterior cruciate ligament reconstruction

OBJECTIVE

To determine the role of limb dominance on energy absorption contribution (EAC) during a jump landing (JL) task at return to sport (RTS) after ACL-R.

DESIGN

Cross-sectional study.

SETTING

Clinical Research Laboratory.

PARTICIPANTS

One hundred eight participants (age = 16.19 ± 1.74, Height = 172.25 ± 9.96 cm, Weight = 72.61 ± 15.48 kg).

MAIN OUTCOME MEASURES

Participants were grouped into two groups: those who injured their dominant limb ACL (D-ACL) and those who injured their non-dominant limb ACL (ND-ACL). A multiple analysis of variance (MANOVA) was used to assess for between group differences in EAC across the three joints.

RESULTS

In the surgical limb, D-ACL demonstrated smaller hip (D-ACL = 32.23 ± 10.44%, ND-ACL = 69.68 ± 8.51%, p < 0.008) and greater knee (D-ACL = 45.86 ± 10.36%, ND-ACL = 9.41 ± 5.68%, p < 0.008) EAC than ND-ACL. In the non-surgical limb, D-ACL demonstrated greater hip (D-ACL = 62.59 ± 9.03%, ND-ACL = 25.95 ± 7.15%, p < 0.008), and smaller knee (D-ACL = 13.79 ± 5.57%, ND-ACL = 58.01 ± 7.86%, p < 0.008), EAC than ND-ACL.

CONCLUSION

After ACL-R, eccentric loading strategies during a JL task at RTS are different depending upon limb dominance. D-ACL demonstrated a greater knee loading strategy on the surgical side compared to ND-ACL.

Relationship between pre- and post-operative isokinetic strength after ACL reconstruction using hamstring autograft

BACKGROUND

Anterior cruciate ligament (ACL) ruptures are of major concern in sports. As mostly young and active individuals are affected there is an emphasis on the rapid and safe return to sports (RTS). Strengthening the ventral and dorsal thigh muscles is a prerequisite for a successful RTS after ACL reconstruction (ACLR), as persistent muscle weakness may increase the incidence for secondary injuries and impair performance. Aiming to increase evidence on the importance of preoperative muscle strength and the coaching of patients, the purpose of this study is to compare thigh muscle strength pre- and post-operatively after ACLR.

METHODS

We performed a retrospective analysis of 80 patients with primary, isolated ACLR using a four-stranded hamstring autograft. We performed bilateral isokinetic concentric strength measurement (60°/s) before and six months after ACLR. Primary outcomes were the maximal knee extension and flexion torque, hamstrings-to-quadriceps ratio (H/Q ratio) and the corresponding limb symmetry indices (LSI). Pearson correlations were calculated for pre- and post-surgical values.

RESULTS

The operated as well as the unaffected leg increased maximal knee extension (+ 18% ± 7% p < 0.05; + 11% ± 5% p < 0.05) and flexion torque (+ 9% ± 5% p < 0.05, + 10% ± 6% p < 0.05) throughout the 6 months of rehabilitation. The H/Q ratio remained unaffected (- 2% ± 3% p = 0.93; - 4% ± 4% p = 0.27). LSI of knee extension strength increased significantly (6% ± 3% p < 0.05), while flexion strength remained unaffected (+ 2% ± 4% p = 0.27). Positive correlations underline the interrelationship between the strength pre- and post-surgery for the knee extension (r = 0.788 p < 0.05) and knee flexion strength (r = 0.637 p < 0.05) after ACLR.

CONCLUSIONS

Preoperative leg extension and flexion strength normalized to body mass are strongly correlated to postoperative strength performance after ACLR. Therefore, pre-operative quadriceps and hamstring muscle strength deficits may have a significant negative impact on functional performance following ACLR. This emphasizes the need for intensive preoperative screening and subsequent treatment to achieve the best possible preoperative leg strength before ACLR.

TRIAL REGISTRATION

DRKS00020210 .

Longitudinal assessments of balance and jump-landing performance before and after anterior cruciate ligament injuries in collegiate athletes

The purpose was to quantify the effect of an anterior cruciate ligament (ACL) injury on balance and jump-landing performance and bilateral asymmetries. Among 500 collegiate athletes who performed a reaching test and a double-leg counter-movement jump-landing test at baseline, 8 male and 6 female athletes suffered ACL injuries. In the follow-up, they performed the reaching test 3 and 6 months after ACL reconstruction (ACLR) and the jump-landing test 6 months after ACLR. Less reaching distances for the injured leg and increased reaching distance asymmetries were observed 3 and 6 months after ACLR compared to baseline. Less peak jumping and landing forces for the injured leg and increased jumping and landing force asymmetries were found 6 months after ACLR compared to baseline. The decreased performance of the injured leg and increased asymmetries may contribute to the high ACL re-injury rates. Baseline assessments would be useful for establishing an individual's pre-injury performance.

Normalized Hip and Knee Strength in Two Age Groups of Adolescent Female Soccer Players

Hannon, JP, Wang-Price, S, Garrison, JC, Goto, S, Bothwell, JM, and Bush, CA. Normalized hip and knee strength in two age groups of adolescent female soccer players. J Strength Cond Res XX(X): 000-000, 2019-Limb symmetry strength measures are used for clinical decision-making considering when an athlete is ready to return to sport after anterior cruciate ligament (ACL) injuries. However, changes in bilateral muscle strength occur after ACL injury resulting in potentially altered limb symmetry calculations. Adolescent female soccer players are at increased risk of sustaining ACL injuries. Published age and sex-matched strength values in this population may be of benefit to clinicians to improve clinical decision-making. The purpose of this study was to establish normative hip and knee strength data of both the dominant and nondominant limbs in adolescent female soccer players. Sixty-four female soccer players (ages 10-18) were enrolled in this study. Subjects were divided by age into 2 groups (group 1: 10-14 years; group 2: 15-18 years). Subjects underwent Biodex isokinetic strength testing at 60°·s and 180°·s to assess quadriceps and hamstring strength. Isometric hip strength (abduction and external rotation) was measured using a hand-held dynamometer. No significant differences were found between groups on either limb in regards to quadriceps or hamstring strength. No significant differences were found between groups on either limb for hip external rotation strength. Significant differences in hip abduction strength were found between groups on the dominant (group 1: 0.21 ± 0.04; group 2: 0.18 ± 0.04; p = 0.014) and nondominant (group 1: 0.21 ± 0.05; group 2: 0.18 ± 0.05; p = 0.019) limbs. The results of this study shed light on normative strength values for a high-risk injury population.

Knee Loading After ACL-R Is Related to Quadriceps Strength and Knee Extension Differences Across the Continuum of Care

Background:

Quadriceps strength and knee extension are believed to be important in the ability to effectively load the knee after anterior cruciate ligament (ACL) reconstruction (ACL-R).

Purpose:

To compare quadriceps strength (QUADS), side-to-side knee extension difference (ExtDiff), and knee energy absorption contribution (EAC) in patients preoperatively, 12 weeks postoperatively, and at return to sport (RTS). A secondary aim was to determine how the factors of QUADS and ExtDiff contributed to the ability to load the knee (knee EAC) at each of the 3 time points.

Study Design:

Case series; Level of evidence, 4.

Methods:

Overall, 41 individuals (mean ± SD age, 15.95 ± 1.63 years) were enrolled in this study. QUADS, ExtDiff, and knee EAC during a double-limb squat were collected preoperatively, 12 weeks postoperatively, and at RTS. Isokinetic QUADS was collected at 60 deg/s, normalized to body mass, and averaged across 5 trials. Knee extension was measured with a goniometer, and ExtDiff was calculated for analyses. Knee EAC was measured during double-limb squat descent and was calculated as a percentage of total energy absorption for the limb. Observations were obtained from both the surgical and nonsurgical limbs at the 3 time points. A mixed regression model with random intercept to compare change over the 3 time points was used, and a model selection was conducted with Akaike information criteria. Significance was set at P < .05.

Results:

Surgical limb QUADS was significantly lower preoperatively (mean ± SD, 1.37 ± 0.49 N·m/kg; P = .0023) and at 12 weeks (1.11 ± 0.38 N·m/kg; P < .0001) than at RTS (1.58 ± 0.47 N·m/kg). Nonsurgical limb QUADS was also significantly lower preoperatively (2.01 ± 0.54 N·m/kg; P < .0256) and at 12 weeks (2.03 ± 0.48 N·m/kg; P < .0233) than at RTS (2.18 ± 0.54 N·m/kg). Knee EAC for the surgical limb was significantly lower at 12 weeks than at RTS (40.98% ± 13.73% vs 47.50% ± 12.04%; P < .0032), and ExtDiff was significantly greater preoperatively than at RTS (–2.68° ± 3.19° vs –0.63° ± 1.43°; P < .0001). Preoperatively, QUADS for both the surgical (P < .0003) and nonsurgical (P = .0023) limbs was a significant predictor of surgical limb knee EAC, explaining 33.99% of the variance. At 12 weeks, surgical limb QUADS was a significant predictor (P < .0051) of surgical limb knee EAC, explaining 18.83% of the variance. At RTS, ExtDiff was a significant predictor (P = .0201) of surgical limb knee EAC, explaining 12.92% of the variance.

Conclusion:

The ability to load the knee after ACL injury changes across the continuum of care and is related to QUADS and ExtDiff. These results provide clinicians with insight into potential contributing factors that may limit knee loading during the rehabilitation process.

Contact times of change-of-direction manoeuvres are influenced by age and the type of sports: a novel protocol using the SpeedCourt® system

PURPOSE

Side-to-side asymmetry in side-cutting manoeuvres is a known risk factor for severe knee injury. Potential leg asymmetry during ground contact times of different change-of-direction manoeuvres was evaluated in athletes by means of the recently developed SpeedCourt^® system. The hypotheses were that ground contact times and the limb symmetry index are affected by age and the type of sports.

METHODS

One-hundred and sixty-five athletes (149 men, 16 women, age 16.5 ± 5.1) of popular team sports such as football, team handball and baseball were assessed by means of three different tests [side-hop, lateral change-of-direction (COD) and diagonal COD] using the SpeedCourt^® system. Analysis included the factors age, sex, type of sports, ground contact time, leg symmetry index and limb dominance.

RESULTS

During lateral but not diagonal COD tests, football players had shorter contact times than players of team handball (p = 0.026) and baseball (p = 0.015) of the same age group. The side-hop tests yielded differences in the leg symmetry index between players < 16 years and players > 16 years (p < 0.01). Mean ground contact time differed in each of the side-hop, lateral COD and diagonal COD tests (143.5 ± 20.0 vs. 256.2 ± 66.1 vs. 320.4 ± 55.0). Contact times and test durations of side-hop, lateral COD and diagonal COD tests were shorter for older players (p < 0.01).

CONCLUSIONS

Ground contact times of side-hop and change-of-direction manoeuvres are influenced by age, the type of sports and limb dominance. Such information is fundamental for future sports medicine research and needs to be considered in pre-season screening or when used as a criterion for return-to-competition of players with previous severe knee injury. Assessment of change-of-direction manoeuvres should be included in future return-to-competition test batteries.

LEVEL OF EVIDENCE

III.

Bilateral Alterations in Running Mechanics and Quadriceps Function Following Unilateral Anterior Cruciate Ligament Reconstruction

BACKGROUND

Following anterior cruciate ligament reconstruction (ACLR), individuals have quadriceps muscle impairments that influence gait mechanics and may contribute to an elevated risk of knee osteoarthritis.

OBJECTIVES

To compare running mechanics and quadriceps function between individuals who have undergone ACLR and those in a control group, and to evaluate the association between quadriceps function and running mechanics.

METHODS

In this controlled, cross-sectional laboratory study, 38 individuals who previously underwent primary unilateral ACLR (mean ± SD time since reconstruction, 48.0 ± 25.0 months) were matched to 38 control participants based on age, sex, and body mass index, and underwent assessments of quadriceps muscle performance and running biomechanics. Quadriceps muscle performance was assessed via isokinetic and isometric knee extension peak torque and rate of torque development (RTD) over 2 time frames: 0 to 100 milliseconds (RTD100) and 0 to 200 milliseconds (RTD200). Running evaluation included assessment of the knee flexion angle (KFA), knee extension moment (KEM), rate of knee extension moment (RKEM), vertical instantaneous loading rate, and vertical impact peak.

RESULTS

On average, there was a smaller KFA (P = .016) in the involved limb compared to the uninvolved limb in the ACLR group. Compared to limbs in the control group, involved limbs in the ACLR group had lower RTD100 (P = .015), lower peak torque at 60°/s (P = .007), lower peak torque at 180°/s (P = .016), smaller KFA (P<.001), lower KEM (P = .001), lower RKEM (P = .004), and higher vertical instantaneous loading rate (P = .016). Compared to limbs in the control group, uninvolved limbs in the ACLR group had lower RTD100 (P = .003), lower peak torque at 60°/s (P = .017), and smaller KFA (P = .01). For the involved limbs in the ACLR group, there was a low correlation between isokinetic peak torque at 180°/s and RKEM (r = 0.38, P = .01), and a negligible correlation between RTD100 and RKEM (r = 0.26, P<.05). No differences were found in isometric strength for any comparison.

CONCLUSION

Individuals who have undergone ACLR have bilateral alterations in running mechanics that are weakly associated with diminished quadriceps muscle performance. J Orthop Sports Phys Ther 2018;48(12):960-967. Epub 22 Jul 2018. doi:10.2519/jospt.2018.8170.

Participants at three months post-operative anterior cruciate ligament reconstruction (ACL-R) demonstrate differences in lower extremity energy absorption contribution and quadriceps strength compared to healthy controls

BACKGROUND

The purpose of this study was to compare hip and knee energy absorption contribution (EAC) during a double limb squat (DLS) and quadriceps strength in patients three months post-operative ACL-R versus matched healthy controls.

METHODS

Twenty-four ACL-R participants (Age = 15.5 ± 1.3 yrs; Ht = 1.66 ± .07 m; Mass = 66.3 ± 15.5 kg) were compared to 24 age, sex, limb, and activity-matched healthy controls (Age = 15.5 ± 1.2 yrs; Ht = 1.65 ± .08 m; Mass = 59.0 ± 9.8 kg). Lower extremity biomechanical data was collected at three months post-operative ACL-R during five consecutive DLS. EAC was calculated during DLS descent. Isokinetic quadriceps strength was collected at 60°/s. Normalized quadriceps peak torque (QUADS) was averaged across five trials. Independent t-tests examined differences in group hip and knee EAC during each task. Separate Pearson product-moment correlations examined the relationship between QUADS and hip and knee EAC during the DLS.

RESULTS

ACL-R demonstrated greater injured limb hip EAC (46.4 ± 16.0) than Healthy (31.7 ± 11.0) during a DLS (p = 0.001). ACL-R demonstrated less injured limb knee EAC (42.7 ± 14.6) than Healthy (60.6 ± 8.9) during DLS (p < 0.001). No differences were seen between uninjured limb hip (ACL-R = 0.0 ± 14.2; Healthy = 33.4 ± 9.1, p = 0.629) or knee (ACL-R = 56.9 ± 15.6; Healthy = 59.1 ± 9.8, p = 0.561) EAC and matched limbs. ACL-R injured limb QUADS was decreased compared to Healthy (ACL-R = 1.1 ± 0.5; Healthy = 2.0 ± 0.5, p < 0.001). No differences were seen in QUADS on the uninjured and matched limbs (ACL-R = 2.0 ± 0.6; Healthy = 1.9 ± 0.5, p = 0.894). There was a weak, negative correlation between injured limb QUADS and hip EAC (r = -0.471, p = 0.001) and moderate, positive correlation between injured limb QUADS and knee EAC (r = 0.615, p < 0.001).

CONCLUSIONS

ACL-R participants demonstrate different eccentric loading strategies during a DLS at three months postoperative compared to matched healthy controls.