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Introduction: Recently, there has been a call for vertical jump testing via force–plate analysis to be included in the assessment of individuals after anterior cruciate ligament reconstruction (ACLR) and as part of return-to-play criteria. However, a synthesis of current literature is needed to help guide clinicians on what tests to perform, which force–plate metrics to assess, and how these may change over the time course of rehabilitation. Methods: Four online databases were searched from inception to July 2022. The Downs and Black checklist was used to assess study quality. Multilevel meta-analyses and meta-regressions were undertaken in conjunction with a best evidence synthesis. Results: Forty-two articles were included, capturing 2375 participants with a history of ACLR. Reconstructed limbs displayed 1) lower peak eccentric forces, concentric forces, landing forces, and lower eccentric and concentric impulses (standardized means difference [SMD] = −1.84 to −0.46) than uninjured contralateral limbs during bilateral countermovement jumps (CMJ) and drop vertical jumps (DVJ); 2) lower jump heights and reactive strength indices (RSI), and longer contact times than uninjured contralateral limbs during unilateral CMJ and DVJ (SMD = −0.86 to 0.26); and 3) lower jump heights, RSI, and longer contact times during bilateral and unilateral CMJ, and unilateral DVJ, than uninjured controls (SMD = −1.19 to 1.08). Meta-regression revealed that time postsurgery was a significant moderator (P < 0.05) for 1) bilateral CMJ height, peak concentric force, and peak landing force; 2) between-limb differences in unilateral CMJ height; and 3) differences in unilateral DVJ height, RSI, and contact time between reconstructed limbs and healthy controls with no history of injury. Conclusions: Individuals with a history of ACLR display chronic deficits in vertical jumping performance during a range of bilateral and unilateral tasks, which may have implications for return-to-play criteria and the design of interventions targeted at restoring long-term deficits in explosive lower limb strength after ACLR. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to test the hypothesis that common weight-bearing exercises generate higher lower-limb muscle forces but do not increase medial tibiofemoral contact force (MTCF) when compared with walking in people with medial knee osteoarthritis and varus malalignment. Methods: Twenty-eight participants 50 yr or older with medial knee osteoarthritis and varus malalignment were recruited from the community. Three-dimensional lower-body motion, ground reaction forces, and surface EMG from 12 lower-limb muscles were acquired during five squat, lunge, single-leg heel raise, and walking trials, performed at self-selected speeds. An EMG-informed neuromusculoskeletal model with subject-specific bone geometry was used to estimate muscle forces (N) and body weight (BW)–normalized MTCF. The peak forces for muscle groups (knee extensors, knee flexors, ankle plantar flexors, and hip abductors) and peak MTCF were compared with walking using a multivariate analysis of variance model. Results: There was a significant main effect (P < 0.001). Post hoc tests (mean difference (95% confidence intervals)) showed that, compared with walking, participants generated higher peak knee extensor and flexor forces during squatting (extensor: 902 N (576 to 1227 N), flexor: 192 N (9.39 to 375 N)) and lunging (extensor: 917 N (604 to 1231 N), flexor: 496 N (198 to 794 N)), and lower peak hip abductor force during squatting (−1975 N (−2841 to −1108 N)) and heel raises (−1217 N (−2131 to −303 N)). Compared with walking, MTCF was lower during squatting (−0.79 BW (−1.04 to −0.53 BW)) and heel raises (−0.27 BW (−0.50 to −0.04 BW)). No other significant differences were observed. Conclusions: Participants generated higher peak knee flexor and extensor forces during squatting and lunging but did not increase peak MTCF compared with walking. Clinicians can use these findings to reassure themselves and patients that weight-bearing exercises in these positions do not adversely increase forces within the osteoarthritic joint compartment. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to determine if a preseason field-based test battery was prospectively associated with noncontact anterior cruciate ligament (ACL) injury in elite female footballers. Methods: In total, 322 elite senior and junior female Australian Rules Football and soccer players had their isometric hip adductor and abductor strength, eccentric knee flexor strength, countermovement jump (CMJ) kinetics, and single-leg hop kinematics assessed during the 2019 preseason. Demographic and injury history details were also collected. Footballers were subsequently followed for 18 months for ACL injury. Results: Fifteen noncontact ACL injuries occurred during the follow-up period. Prior ACL injury (odds ratio [OR], 9.68; 95% confidence interval (95% CI), 2.67–31.46), a lower isometric hip adductor to abductor strength ratio (OR, 1.98; 95% CI, 1.09–3.61), greater CMJ peak take-off force (OR, 1.74; 95% CI, 1.09–3.61), and greater single-leg triple vertical hop average dynamic knee valgus (OR, 1.97; 95% CI, 1.06–3.63) and ipsilateral trunk flexion (OR, 1.60; 95% CI, 1.01–2.55) were independently associated with an increased risk of subsequent ACL injury. A multivariable prediction model consisting of CMJ peak take-off force, dynamic knee valgus, and ACL injury history that was internally validated classified ACL injured from uninjured footballers with 78% total accuracy. Between-leg asymmetry in lower limb strength and CMJ kinetics were not associated with subsequent ACL injury risk. Conclusions: Preseason field-based measures of lower limb muscle strength and biomechanics were associated with future noncontact ACL injury in elite female footballers. These risk factors can be used to guide ACL injury screening practices and inform the design of targeted injury prevention training in elite female footballers. [ABSTRACT FROM AUTHOR]

Purpose: Identification of the biomechanical alterations in individuals with symptomatic femoroacetabular impingement (FAI) is critical to understand the pathology and inform treatments. Yet hip function in this condition is poorly defined. Squatting requires large hip flexion range and involves motion toward the position of hip impingement; thus, it is likely to expose modified biomechanics in these individuals. This study aimed to determine whether hip and pelvis biomechanics differ between individuals with and without symptomatic FAI during an unconstrained deep squat and a constrained squat designed to limit compensation by the pelvis and trunk. Methods: Fifteen participants with symptomatic cam-type or combined (cam plus pincer) FAI who were scheduled for arthroscopic surgery and 14 age- and sex-matched controls without FAI underwent three-dimensional motion analysis during the two squatting tasks. Trunk, pelvis, and hip kinematics and hip kinetics were compared between groups. Results: There were no between-group differences in normalized squat depth for either task. Descent speed was slower for the FAI group during the unconstrained squat (P < 0.05). During the constrained squat, individuals with FAI demonstrated greaterpelvic rise (P = 0.01) andhip adduction (P = 0.04) on the symptomatic side than controls. The hip external rotation moment was less in FAI patients during descent (P = 0.04), as was transverse plane hip angle variability (P = 0.04). Conclusions: Individuals with symptomatic FAI can squat to a depth comparable with controls, regardless of task design. When the task is constrained, FAI patients demonstrate greater ipsilateral pelvic rise and maintain a more adducted hip position, which may coincide with a compensatory strategy to avoid end range flexion as the hip approaches impingement. These biomechanical alterations may put additional stress on adjacent regions and have relevance for rehabilitation. [ABSTRACT FROM AUTHOR]

Introduction: We compared the 12-months effects of arthroscopic surgery and physiotherapist-led care for femoroacetabular impingement (FAI) syndrome on the time-varying magnitude of hip contact force and muscle contributions to hip contact force during walking., Methods: Secondary analysis was performed on thirty-seven individuals with FAI syndrome who received biomechanical assessment before and 12-months following either arthroscopic surgery (n = 17) or physiotherapist-led care (Personalised Hip Therapy, PHT) (n = 20). At both time points, three-dimensional whole-body motions, ground reaction forces, and surface electromyograms (n = 14) were acquired during overground walking. A neuromusculoskeletal model was used to determine hip contact force and muscle contributions to hip contact force. Two-way repeated measures analyses of variance, implemented through statistical parametric mapping, were used to assess interactions between, and main effects of, treatment (arthroscopy vs. PHT) and time (baseline vs. follow-up) on time-varying magnitude of hip contact force and muscle contributions to hip contact force. Effects were reported as mean differences (normalized to bodyweight, BW) with 95% confidence intervals [95% CI, lower, upper bound]., Results: For both treatment groups, hip contact force was larger at 12-months compared to their respective baseline (mean increase across stride, arthroscopy: 0.97 BW [95% CI 0.49, 1.46] p < .001; PHT: 1.05 BW [95% CI 0.68, 1.43] p < .001), however, no interaction effects were found. For both treatment groups, hip flexor, adductor, and abductor muscle groups made greater contributions to hip contact force after 12-months compared to baseline, while hip extensors made smaller contributions., Conclusions: Compared to baseline, both treatments resulted in 12-months increases in hip contact force during walking caused by larger flexor, adductor, and abductor muscle forces at follow-up. At 12-months, hip contact force magnitude remained different normative values reported for healthy individuals, indicating neither treatment fully restored hip biomechanics., Competing Interests: Conflict of Interest and Funding Source: DJH is a consultant to Pfizer, Lilly, TLCBio, and Merck Serono and he and KLB are supported by Australian National Health and Medical Research Council Investigator Grants. For the remaining authors, no conflicts of interest were declared. This work was supported by the Australian National Health and Medical Research Council [grant APP1069278, 2014]. The funding source was not involved in study design, data collection, data analysis or interpretation of results, writing of the manuscript or the decision to submit the article for publication. The authors have no conflicts of interest to disclose., (Copyright © 2024 by the American College of Sports Medicine.)