Effects of neuromuscular training on knee proprioception in individuals with anterior cruciate ligament injury: a systematic review and GRADE evidence synthesis

Conservative treatment versus surgical reconstruction for ACL rupture: A systemic review

Background

Anterior cruciate ligament (ACL) rupture is a prevalent sports injury with rising rates attributed to increased population participation in sports activities. ACL rupture can lead to severe knee complications including cartilage damage, torn meniscus, and osteoarthritis. Current treatment options include conservative measures and surgical interventions. However, debates persist regarding the optimal approach.

Purpose

This analysis intended to compare the function, knee stability, and incidence rate of secondary surgery between conservative and surgical treatments in ACL rupture patients.

Methods

A systematic search was performed via Embase, Ovid Medline, PubMed, Cochrane Library, Web of Science, and Google Scholar for reporting outcomes of conservative and surgical treatments after ACL rupture. The outcomes included patient-reported outcome measures (PROMs), knee stability, the need for secondary meniscal surgery, delayed ACL reconstruction surgery, and revision ACL reconstruction surgery. Outcomes were analyzed using mean differences or odd ratios (OR) with 95 % CIs.

Results

11 studies were included with 1516 patients. For PROMs, our evidence indicated no differences in KOOS Pain, KOOS Symptoms, KOOS Sport/Rec, KOOS ADL, and KOOS QOL. (all p > 0.05). for knee stability, pivot shift (OR, 0.14; p < 0.001), Lachman test (OR, 0.06; p < 0.001), and tibia translation (p < 0.001) were evaluated, and the available evidence favored surgical treatment over conservative treatment. For the incidence rate of any secondary surgery after the first diagnosis, the surgical group showed a lower rate of meniscal surgery with statistical significance (OR, 0.37; p < 0.001). The average rate of revision ACL reconstruction is 5.80 %, while the rate of delayed ACL reconstruction after conservative treatment is 18.51 %.

Conclusion

Currently, there is insufficient empirical evidence to advocate a systematic surgical reconstruction for any patient who tore his ACL. This review found no differences in function outcomes between conservative and surgical treatments. Regarding knee stability and secondary meniscal surgery, the results prefer the surgical treatments. The occurrence rate of revision and delayed ACL reconstruction are non-negligible factors that must be fully understood by both surgeons and patients before choosing a suitable treatment.

Application of sensory and motor training in AIDET communication mode in patients after knee arthroplasty

BACKGROUND

Patients with knee arthroplasty often have problems such as slow recovery of knee function, which may cause negative emotions and affect their postoperative rehabilitation. The application of sensory and motor training in the Acknowledge, Introduce, Duration, Evaluation, Thank You (AIDET) communication mode in patients after knee arthroplasty can provide reference for the selection of postoperative rehabilitation training measures.

AIM

To explore the sensory and motor training effects in AIDET communication mode on knee function recovery and resilience of patients after knee arthroplasty.

METHODS

One hundred patients who underwent knee arthroplasty at our hospital between January 2022 and January 2024 were randomly divided into two groups. The control group (n = 50) received routine rehabilitation training. In the observation group (n = 50), the AIDET communication mode was used to perform sensory and motor training, in addition to routine rehabilitation training. The rehabilitation training was administered for 8 weeks. After surgery, knee function, balance ability, walking ability, proprioception, and resilience were compared between the two groups.

RESULTS

The New York Hospital for Special Surgery knee scores of the observation group at the time of discharge and 8 weeks after intervention were (65.23 ± 6.84, 84.53 ± 5.27), which was higher than those of the control group (61.03 ± 7.15, 74.92 ± 6.52) (P < 0.05). The balance ability of the observation group at the time of discharge and 8 weeks after the intervention was higher than that of the control group, the time of time up to go test was shorter than that of the control group, and proprioceptive function was higher than that of the control group (P < 0.05). The resilience level in the observation group after the intervention was higher than that in the control group (P < 0.05).

CONCLUSION

Sensory and motor training in AIDET communication mode promotes knee function recovery of patients after knee arthroplasty, improves their limb walking ability and balance function, and increases their resilience level.

Acute neuromuscular responses to whole-body vibration in healthy individuals: A systematic review

Whole-body vibration (WBV) training has been employed alongside conventional exercise like resistance training to enhance skeletal muscle strength and performance. This systematic review examines the evidence regarding the effect of WBV on muscle activity, strength, and performance in healthy individuals. The Academic Search Ultimate, CINAHL, Cochrane CENTRAL, PubMed, ProQuest One Academic and SCOPUS databases were searched from 1990 to April 2023 to retrieve relevant studies. Methodological quality was assessed using the Modified Downs and Black checklist, while the level of evidence was evaluated through the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) tool. Even though the quality of the included studies was moderate to high, the level of evidence was very low owing to serious concerns with three or more GRADE domains (risk of bias, inconsistency, indirectness, imprecision, and publication bias) for each outcome of interest across studies. The review suggests that in WBV training, using moderate to high vibration frequencies (25-40 Hz) and high magnitudes (3-6 mm) can enhance muscle activation and strength in pelvis and lower limb muscles. However, findings regarding WBV effect on muscle performance measures were inconsistent. Future research with robust methodology is necessary in this area to validate and support these findings.

Acute effects of Nordic hamstring exercise on hip and knee joints proprioception

BACKGROUND AND OBJECTIVES

Nordic Hamstring Exercise (NHE) is one of the best exercises proposed for injury prevention of hamstring muscles. However, its effects on lower extremity proprioception are unclear. The aim of this study was to investigate the immediate effects of a single bout of NHE on hip and knee joints' proprioception.

METHODS

Forty collegiate male soccer players participated in this study with a mean age of 22.85 ± 1.82 years and were randomized into either control (n = 20) or experimental (n = 20) groups. Each subject participated in pre-test measurements in which hip and knee active joints position sense (JPS) were assessed in standing and lying tasks using the image-capturing method. The experimental group then performed three sets of NHE with 10 repetitions in each set, while the control group rested for 10 min. Paired and independent t-tests were used for calculating the differences within and between groups on SPSS software, respectively. The level of significance was P ≤ 0.05.

RESULTS

Hip JPS in the lying task and knee JPS in both of the standing and lying tasks were impaired significantly after performing a single bout of NHE (P ≤ 0.05). However, the effects of this exercise on hip JPS in the standing task were not significant (P ≥ 0.05).

CONCLUSIONS

NHE performing with three sets of 10 repetitions can significantly impair hip and knee JPS immediately after exercise and reduce the proprioception acuity of the lower limbs. It is recommended to perform this exercise at a time rather than before training or match sessions.

Effect of whole-body vibration frequency on objective physical function outcomes in healthy young adults: Randomized clinical trial

INTRODUCTION

Whole-body vibration (WBV) is used to improve muscle function but is important to know if doses can affect the objective function outcomes.

OBJECTIVE

To compare the effect of two frequencies of WBV on objective physical function outcomes in healthy young adults.

METHODS

Forty-two volunteers were randomized into three groups: sham group (SG), and WBV groups with 30 (F30) and 45 Hz (F45). A 6-week WBV intervention protocol was applied by a vibrating platform twice a week, with the platform turn-off for SG and with two frequencies according to group, 30 or 45 Hz. The objective physical functions outcomes assessed were the proprioceptive accuracy, measured by proprioceptive tests, and quasi-static and dynamic balances, measured by Sensory Organization Test (SOT) and Y Balance Test, respectively. The outcomes were assessed before and after the WBV intervention. We used in the results comparisons, by GzLM test, the deltas percentage.

RESULTS

After the intervention, no statistical differences were observed in percentage deltas for any outcomes (proprioceptive accuracy, quasi-static and dynamic balances).

CONCLUSION

Objective physical function outcomes, after the 6-week WBV protocol, did not present statistically significant results in any of the intervention groups (F30 or F45) and SG.

Effects of contrast water therapy on proprioception of the knee joint and degree of fatigue in sprinters after high intensity training

OBJECTIVE

To investigate the effect of contrast water therapy on proprioception of the knee joint and indicators associated with fatigue in sprinters after high intensity training.

METHODS

A total of 40 sprinters were selected and divided into an observation group and a control group. The observation group got 14 minutes of contrast water therapy, while the control group took 14 minutes of sitting rest after training. The knee position sense, muscle force sense, joint reaction angle to release, knee joint function, and indictors associated with fatigue were evaluated before and after exercise at different time points.

RESULTS

At 24 h, 48 h, and 72 h after exercise, the active position sense and muscle force sense of the control group were significantly lower than those of the observation group (all P<0.05). At 48 h after exercise, the passive position sense of the control group was significantly lower than that of the observation group (all P<0.05). At 24 h and 48 h after exercise, the joint reaction angle to release of the control group was significantly greater than that of the observation group (all P<0.05). Additionally, the IKDC2000 and Lysholm scores after interference in the observation group were greater than those of the control group (all P<0.05). The indicators associated with fatigue after interference in the observation group were significantly lower than those of the control group (all P<0.05).

CONCLUSION

Contrast water therapy can effectively alleviate muscle force sense, promote muscle proprioception, improve knee joint function, and enhance recovery from fatigue.

Comparison of Functional Outcomes after Anterior Cruciate Ligament Reconstruction with Meniscal Repair for Unstable versus Stable Meniscal Tears

This study aimed to compare functional outcomes including knee muscle strength in the quadriceps and hamstrings, and proprioception, assessed through dynamic postural stability (overall stability index [OSI]) and self-reported outcomes in the operated and non-operated knees between anterior cruciate ligament reconstruction (ACLR) with meniscal repair for unstable (root and radial tears) and stable (longitudinal, horizontal, and bucket handle tears) meniscal tears. A total of 76 patients were randomly selected (41 with ACLR with meniscal repair for unstable meniscal tears and 35 with ACLR with meniscal repair for stable meniscal tears) at three different time points (preoperative, 6 months, and 12 months). Repeated measures analysis of variance was used to investigate the differences in outcomes for between-subject and within-subject factors. In the operated knees, there were no significant differences for functional outcomes between the two groups (all p > 0.05). In the non-operated knees, a significant difference was observed for the OSI between the two groups, which was significantly higher in ACLR with meniscal repair for unstable meniscal tears than for stable meniscal tears at 6 months (p < 0.001). Multiple linear regression analysis showed that age (p = 0.027), preoperative OSI in the operated knees (p = 0.005), and postoperative OSI in the operated knees at 6 months (p = 0.002) were significant and independent predictors for OSI in the non-operated knees at 6 months postoperatively. Therefore, while no differences were observed in functional outcomes between the two groups in the operated knees, dynamic postural stability was poorer at 6 months postoperatively in the non-operated knees of patients with ACLR with meniscal repair for unstable meniscal tears. Furthermore, a significant correlation was observed between preoperative/postoperative dynamic postural stability in the operated knees and postoperative dynamic postural stability in the non-operated knees. Hence, we recommend incorporating balance exercises for both knees in post-surgical rehabilitation, particularly for patients with unstable meniscal tears.

Known-group validity of passive knee joint position sense: a comparison between individuals with unilateral anterior cruciate ligament reconstruction and healthy controls

BACKGROUND

Knee joint position sense (JPS) might be negatively affected after injuries to the anterior cruciate ligament (ACL). Recent systematic reviews suggest further investigation of psychometric properties, including validity, of knee JPS tests following ACL reconstruction (ACLR). This study investigated the known-group validity by comparing knee JPS errors between individuals who underwent unilateral ACLR and healthy controls.

METHODS

This cross-sectional study involved 36 men, including 19 after ACLR (ACLR group) and 17 healthy controls (control group). In both groups, the absolute error (AE), constant error (CE) and variable error (VE) of passive knee JPS were calculated in the flexion and extension directions, for two target angles (30° and 60° flexion) per direction. Discriminative validity was evaluated by comparing JPS errors between the operated and non-operated knees in the ACLR group. Known-group validity was evaluated by comparing JPS errors between the operated knees in the ACLR group and the asymptomatic non-dominant knees of healthy controls.

RESULTS

Mean AE, CE and VE for all tests were 4.1°, - 2.3° and 3.6° for the operated knees in the ACLR group, 5.5°, - 2.6° and 3.3° for the non-operated knees in the ACLR group and 4.6°, - 2.6° and 3.3° for the non-dominant knees in the control group, respectively, regardless of the test direction and target angle. The operated knees in the ACLR group did not show significantly greater JPS errors compared to the contralateral knees in the ACLR group and to the non-dominant knees in the control group (p ≥ 0.05). On the other hand, the non-operated knees showed significantly greater AE for the 0°-60° flexion test (p = 0.025) and CE for the 0°-30° flexion test (p = 0.024) than the operated knees in the ACLR group. JPS errors did not significantly differ in the operated knees in the ACLR group based on the direction of movement and the target angle. However, the errors were significantly higher when the knee was moved through a greater range compared to that of a lesser range between the starting and target angles.

CONCLUSION

The ACLR knees did not show greater passive JPS errors than the contralateral or control knees. The direction of movement and target angle did not influence the JPS acuity after ACLR. However, higher JPS errors were evident when the knee was moved through a greater range compared to a lesser range of motion. Further studies investigating the psychometric properties of standardized JPS tests following ACLR are warranted.

Investigating Knee Joint Proprioception and Its Impact on Limits of Stability Using Dynamic Posturography in Individuals with Bilateral Knee Osteoarthritis-A Cross-Sectional Study of Comparisons and Correlations

(1) Background: Proprioception and limits of stability can significantly impact static and dynamic balance. Knee proprioception and limits of stability may be impaired in individuals with knee osteoarthritis (KOA). Impaired knee proprioception may impact the limits of stability, and understanding the associations between these factors is important for formulating treatment strategies in this population. The objectives of this study are to (a) compare the knee joint position error (JPE) and limits of stability between KOA and asymptomatic individuals and (b) assess the correlation between knee JPE and the limits of stability in KOA individuals. (2) Methods: This cross-sectional study included 50 individuals diagnosed with bilateral KOA and 50 asymptomatic individuals. Knee JPE was measured using a dual digital inclinometer at 25° and 45° of knee flexion (in the dominant and nondominant legs). The limits of stability variables, including reaction time (s), maximum excursion (%), and direction control (%), were evaluated using computerized dynamic posturography. (3) Results: The magnitude of the mean knee JPE is significantly larger in KOA individuals (p < 0.001) compared to asymptomatic individuals assessed at 25° and 45° of knee flexion in both the dominant and nondominant legs. The limits of stability test showed that KOA group individuals had a longer reaction time (1.64 ± 0.30 s) and reduced maximum excursion (4.37 ± 0.45) and direction control (78.42 ± 5.47) percentages compared to the asymptomatic group (reaction time = 0.89 ± 0.29, maximum excursion = 5.25 ± 1.34, direction control = 87.50 ± 4.49). Knee JPE showed moderate to strong correlations with the reaction time (r = 0.60 to 0.68, p < 0.001), maximum excursion (r = -0.28 to -0.38, p < 0.001) and direction control (r = -0.59 to -0.65, p < 0.001) parameters in the limits of stability test. (4) Conclusions: Knee proprioception and limits of stability are impaired in KOA individuals compared to asymptomatic individuals, and knee JPE showed significant relationships with the limits of stability variables. These factors and correlations may be considered when evaluating and developing treatment strategies for KOA patients.

Multiclass Support Vector Machine improves the Pivot-shift grading from Gerdy's acceleration resultant prior to the acute Anterior Cruciate Ligament surgery

INTRODUCTION

Rotatory laxity acceleration still lacks objective classification due to interval grading superposition, resulting in a biased pivot shift grading prior to the Anterior Cruciate Ligament (ACL) reconstruction. However, data analysis might help improve data grading in the operative room. Therefore, we described the improvement of the pivot-shift categorization in Gerdy's acceleration under anesthesia prior to ACL surgery using a support vector machine (SVM) classification, surgeon, and literature reference.

METHODS

Seventy-five patients (aged 30.3 ± 10.2 years, and IKDC 52.0 ± 16.5 points) with acute ACL rupture under anesthesia prior to ACL surgery were analyzed. Patients were graded with pivot-shift sign glide (+), clunk (++), and (+++) gross by senior orthopedic surgeons. At the same time, the tri-axial tibial plateau acceleration was measured. Categorical data were statistically described, and the accelerometry and categorical data were associated (α = 5%). A multiclass SVM kernel with the best accuracy trained by orthopedic surgeons and assisted from literature for missing data was compared with experienced surgeons and literature interval grading. The cubic SVM classifier achieved the best grading.

RESULTS

The intra-group proportions were different for each grading in the three compared strategies (p < 0.001). The inter-group proportions were different for all comparisons (p < 0.001). There were significant (p < 0.001) associations (Tau: 0.69, -0.28, and -0.50) between the surgeon and SVM, the surgeon and interval grading, and the interval and SVM, respectively.

CONCLUSION

The multiclass SVM classifier improves the acceleration categorization of the (+), (++), and (+++) pivot shift sign prior to the ACL surgery in agreement with surgeon criteria.

Reliability of the active knee joint position sense test and influence of limb dominance and sex

The output of a sensorimotor performance can be measured with the joint position sense (JPS) test. However, investigations of leg dominance, sex and quality measures on this test are limited. Therefore, these potential influencing factors as well as reliability and consistency measures were evaluated for angular reproduction performance and neuromuscular activity during the active knee JPS test in healthy participants. Twenty healthy participants (10 males; 10 females; age 29 ± 8 years; height 165 ± 39 cm; body mass 69 ± 13 kg) performed a seated knee JPS test with a target angle of 50°. Measurements were conducted in two sessions separated by two weeks and consisted of two blocks of continuous angular reproduction (three minutes each block). The difference between reproduced and target angle was identified as angular error measured by an electrogoniometer. During reproduction, the neuromuscular activity of the quadriceps muscle was assessed by surface electromyography. Neuromuscular activity was normalized to submaximal voluntary contraction (subMVC) and displayed per muscle and movement phase. Differences between leg dominance and sex were calculated using Friedman-test (α = 0.05). Reliability measures including intraclass correlation coefficient (ICC), Bland-Altman analysis (bias ± limits of agreement (LoA)) and minimal detectable change (MDC) were analysed. No significant differences between leg dominance and sex were found in angular error and neuromuscular activity. Angular error demonstrated inter-session ICC scores of 0.424 with a bias of 2.4° (± 2.4° LoA) as well as MDC of 6.8° and moderate intra-session ICC (0.723) with a bias of 1.4° (± 1.65° LoA) as well as MDC of 4.7°. Neuromuscular activity for all muscles and movement phases illustrated inter-session ICC ranging from 0.432 to 0.809 with biases between - 2.5 and 13.6% subMVC and MDC from 13.4 to 63.9% subMVC. Intra-session ICC ranged from 0.705 to 0.987 with biases of - 7.7 to 2.4% subMVC and MDC of 2.7 to 46.5% subMVC. Leg dominance and sex seem not to influence angular reproduction performance and neuromuscular activity. Poor to excellent relative reliability paired with an acceptable consistency confirm findings of previous studies. Comparisons to pathological populations should be conducted with caution.

Comparison of proprioception recovery following anterior cruciate ligament reconstruction using an artificial graft versus an autograft

BACKGROUND

To compare proprioception recovery after anterior cruciate ligament reconstruction (ACLR) with a hamstring tendon autograft versus the artificial Ligament Advanced Reinforcement System (LARS).

MATERIAL AND METHODS

Forty patients (9 females, 31 males) with anterior cruciate ligament (ACL) rupture were enrolled in this prospective study. Patients were randomized to two groups, 1) ACLR using a hamstring tendon autograft (n = 20) or 2) ACLR using artificial LARS (n = 20). Proprioception was assessed with knee joint position sense (JPS) passive-passive test at 45° and 75° flexions, with the contralateral healthy knee as a control baseline to calculate the JPS error. Knee JPS absolute error was used as the main outcome variable and defined as the absolute difference between the reproduction and target angles.

RESULTS

JPS error in both groups at 3 months after ACLR was significantly higher than that at 12 months. However, no significant difference in JPS error was detected between the LARS and autograft groups at either 3 or 12 months after ACLR. Analyzing JPS data by grouping patients according to whether ACLR was performed more or less than 1 year following injury regardless of graft type showed a statistically significant difference between the groups at 3 months, but not at 12 months, after ACLR. Patients receiving the graft within 1 year of injury had a lower JPS error than those receiving the graft more than 1 year after injury at 3 months. No complications were associated with either ACLR method.

CONCLUSION

ACLR with a hamstring tendon autograft or LARS artificial graft is similarly safe and effective for recovering knee proprioception.

Rehabilitation And Advances In Surgical Reconstruction For Anterior Cruciate Ligament Insufficiency: What Has Changed Since The 1960s? - State Of The Art

Anterior cruciate ligament (ACL) insufficiency can be disabling, given the physical and sports activity constraints that negatively impact the quality of life. Consequently, surgery is the main approach for most active patients. Nonetheless, ACL reconstruction (ACLR) cannot be successful without adequate preoperative and postoperative rehabilitation. Since the 1960s, post-ACLR rehabilitation has evolved, mainly from advances in surgery, coupled with a better understanding of the biological concepts of graft revascularization, maturation and integration, which have impacted ACL postoperative rehabilitation protocols. However, new technologies do involve a definite learning curve which could affect rehabilitation programs and produce inconsistent results. The development of rehabilitation protocols cannot be defined without an accurate diagnosis of ACL injury and considering the patient's main physical demands and expectations. This article discusses how postoperative rehabilitation following ACLR has changed from the 1960s to now, focussing on surgical technique (type of tendon graft, fixation devices, and graft tensioning), biological concepts (graft maturation and integration), rehabilitation protocols (prevention of ACL injuries, preoperative rehabilitation, postoperative rehabilitation), criteria to return to sports, patient's reported outcomes and outcome. Although rehabilitation plays an essential role in managing ACL injuries, it cannot be fully standardised preoperatively or postoperatively. Preoperative and postoperative rehabilitation should be based on an accurate clinical diagnosis, patients' understanding of their injury, graft tissue biology and biomechanics, surgical technique, the patient's physical demands and expectations, geographical differences in ACL rehabilitation and future perspectives.

Rehabilitation after anterior cruciate ligament and meniscal injuries: a best-evidence synthesis of systematic reviews for the OPTIKNEE consensus

OBJECTIVE

Synthesise evidence for effectiveness of rehabilitation interventions following ACL and/or meniscal tear on symptomatic, functional, clinical, psychosocial, quality of life and reinjury outcomes.

DESIGN

Overview of systematic reviews with Grading of Recommendations Assessment, Development and Evaluation certainty of evidence.

DATA SOURCES

MEDLINE, EMBASE, CINAHL, SPORTDiscus and Cochrane Library.

ELIGIBILITY CRITERIA

Systematic reviews of randomised controlled trials investigating rehabilitation interventions following ACL and/or meniscal tears in young adults.

RESULTS

We included 22 systematic reviews (142 trials of mostly men) evaluating ACL-injured individuals and none evaluating isolated meniscal injuries. We synthesised data from 16 reviews evaluating 12 different interventions. Moderate-certainty evidence was observed for: (1) neuromuscular electrical stimulation to improve quadriceps strength; (2) open versus closed kinetic chain exercises to be similarly effective for quadriceps strength and self-reported function; (3) structured home-based versus structured in-person rehabilitation to be similarly effective for quadriceps and hamstring strength and self-reported function; and (4) postoperative knee bracing being ineffective for physical function and laxity. There was low-certainty evidence that: (1) preoperative exercise therapy improves self-reported and physical function postoperatively; (2) cryotherapy reduces pain and analgesic use; (3) psychological interventions improve anxiety/fear; and (4) whole body vibration improves quadriceps strength. There was very low-certainty evidence that: (1) protein-based supplements improve quadriceps size; (2) blood flow restriction training improves quadriceps size; (3) neuromuscular control exercises improve quadriceps and hamstring strength and self-reported function; and (4) continuous passive motion has no effect on range of motion.

CONCLUSION

The general level of evidence for rehabilitation after ACL or meniscal tear was low. Moderate-certainty evidence indicates that several rehabilitation types can improve quadriceps strength, while brace use has no effect on knee function/laxity.

Thigh muscle co-contraction patterns in individuals with anterior cruciate ligament reconstruction, athletes and controls during a novel double-hop test

Efficient neuromuscular coordination of the thigh muscles is crucial in maintaining dynamic knee stability and thus reducing anterior cruciate ligament (ACL) injury/re-injury risk. This cross-sectional study measured electromyographic (EMG) thigh muscle co-contraction patterns during a novel one-leg double-hop test among individuals with ACL reconstruction (ACLR; n = 34), elite athletes (n = 22) and controls (n = 24). Participants performed a forward hop followed by a 45° unanticipated diagonal hop either in a medial (UMDH) or lateral direction (ULDH). Medial and lateral quadriceps and hamstrings EMG were recorded for one leg (injured/non-dominant). Quadriceps-to-Hamstring (Q:H) ratio, lateral and medial Q:H co-contraction indices (CCIs), and medial-to-lateral Q:H co-contraction ratio (CCR; a ratio of CCIs) were calculated for three phases (100 ms prior to landing, initial contact [IC] and deceleration phases) of landing. We found greater activity of the quadriceps than the hamstrings during the IC and deceleration phases of UMDH/ULDH across groups. However, higher co-contraction of medial rather than lateral thigh muscles during the deceleration phase of landing was found; if such co-contraction patterns cause knee adduction, a putative mechanism to decrease ACL injury risk, during the deceleration phase of landing across groups warrants further investigation.