The limb symmetry index (LSI) is widely used to assess bilateral lower limb recovery and re-injury risk following anterior cruciate ligament reconstruction (ACLR). This study aims to investigate how lower limb muscle strength symmetry influences biomechanical characteristics during the single leg hop test in patients one-year post-ACLR, and to identify the potential impact of muscle strength asymmetry on re-injury risk during landing movements in ACLR patients. Method: Thirty ACLR patients completed isokinetic quadriceps strength testing and single-leg hop tests. Based on quadriceps strength symmetry, they were categorized into a high-symmetry group (LSI > 85%, n = 15) and a low-symmetry group (LSI < 85 %, n = 15). Lower limb biomechanical data during the single-leg jump-landing tests were collected synchronously using a Vicon motion capture system and AMTI force platforms. A two-way repeated measures ANOVA was conducted to examine the effects of group and limb on various outcome measures. (1) A significant interaction effect was observed between limb and group for knee valgus angle. Post-hoc analysis revealed that in the high symmetry group, the valgus angle of the contralateral limb was significantly greater than that of the reconstructed limb (P < 0.01). (2) A significant interaction was also found between limb and group for knee internal rotation moment. Post-hoc analysis showed that in the high-symmetry group, the internal rotation moment of the contralateral limb was significantly greater than that of the reconstructed limb (P = 0.001). In addition, knee extension and valgus moments were significantly greater in the contralateral limb than in the reconstructed limb in both groups (P < 0.01). (3) The peak vertical ground reaction force during the landing phase was significantly greater in the contralateral limb than in the reconstructed limb in both groups (P = 0.001). (1) Compared to the reconstructed limb, the contralateral limb of ACLR patients demonstrated greater knee extension moment, knee valgus moment, and ground reaction force, suggesting an increased risk of secondary anterior cruciate ligament (ACL) injury to the contralateral limb. (2) In the high-symmetry group, the contralateral limb exhibited increased knee valgus angle and internal rotation moment, potentially suggesting a higher susceptibility to ACL re-injury. In conclusion, rehabilitation of the contralateral limb should be equally prioritized in patients following ACLR to ensure comprehensive recovery and to minimize the risk of re-injury.
Zhang et al. (Thu,) studied this question.