Examination of a novel limb symmetry index to discriminate movement strategies during bilateral jump landing in individuals with ACLR and with and without a history of ankle sprains.

INTRODUCTION The Limb Symmetry Index (LSI), computed from kinetic parameters, tracks knee functionality post Anterior Cruciate Ligament Reconstruction (ACLR). However, LSI may lack accuracy in individuals with ACLR and ankle sprains, as it overlooks kinetic chain coordination across lower limb joints. Previous ankle sprains (AS) contribute to altered neuromuscular control in ACLR, emphasizing the need to evaluate within-limb coordination during bilateral tasks to prevent secondary ACL injuries. The effect of Energy Absorption Contribution (EAC) on joint work provides insight into the coordination between joints during observed movements. Thus, the purpose of this study was to validate a novel LSI based on EAC for discriminating movement strategies in bilateral drop vertical jump landing (DVJL) among individuals with ACLR and ACLR-AS METHODS 39 healthy athletes, including 13 healthy controls, 13 ACLR, and 13 ACLR-AS were matched by age, height, weight, sex, sports involvement, and limb dominance. Participants performed five DVJLs with kinematics and ground reaction forces recorded. Individual joint work (M) and EAC were calculated and averaged across the middle three trials to compute the LSI on individual joint work (LSIM) and EAC (LSIEAC). Negative LSI indicates asymmetry toward the nonsurgical limb, while positive LSI indicates asymmetry toward the surgical limb. A 3x2x3 repeated measures analysis of variance was utilized to analyze interactions between groups, the LSI method, and joint. Tukeys LSD post-hoc analyses were used to examine within and between groups (alpha=0.05). RESULTS There was a significant interaction between the group, LSI method, and joint (F4,72=3.216, P=.017). LSIEAC identified significant loading asymmetry at the hip (P=.046) and knee (P=.015) when compared to healthy controls. CONCLUSIONS LSIEAC proved to be the method capable of distinguishing group differences in loading asymmetry at the hip and knee for the ACLR-AS group compared to healthy controls during bilateral DVJL. Overall, LSIEAC provided a more comprehensive insight into the movement strategies employed during DVJL, particularly for individuals with ACLR and ACLR-AS. This emphasizes its suitability for effectively monitoring the rehabilitation progression post ACLR towards RTS. Our findings suggest that clinicians should prioritize computing the LSI based on EAC and assessing the history of ankle sprains for precise RTS decision-making. This approach not only aids in identifying loading asymmetry at the knee and hip but also underscores the critical importance of restoring modified movement strategies in adolescents with ACLR-AS, ultimately reducing the risk of secondary ACL injury following RTS.