Effect of Exercise Therapy on Lower Limb Biomechanical Characteristics in Individuals After Anterior Cruciate Ligament Reconstruction: A Systematic Review and Meta-analysis of Randomized Controlled Trials

Background: Various exercise interventions are recommended to reduce the risk of anterior cruciate ligament (ACL) reinjury after ACL reconstruction (ACLR). However, the extent to which these training interventions influence lower-limb biomechanics in those who underwent ACLR remains unclear. Purpose: To determine whether existing exercise therapies can improve lower-limb biomechanical characteristics after ACLR. Study Design: Systematic review; Level of evidence, 1. Methods: In accordance with the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, we searched PubMed, Embase, Cochrane Library, Web of Science, Scopus, and EBSCO to identify randomized controlled trials investigating the effects of exercise therapy on biomechanical characteristics after ACLR. The control group received conventional rehabilitation training, while the experimental group underwent various types of exercise therapy interventions. Seven kinematic and kinetic parameters were selected as outcome measures, and subgroup analyses were conducted based on testing tasks. The search timeframe spanned from database inception to June 3, 2025. The quality of the included studies was assessed using the Risk of Bias 2.0 tool. A meta-analysis was performed using Review Manager 5.3. Results are presented as standardized mean differences (SMD) with 95% CIs. Results: A total of 1512 studies were identified in the initial search. Twelve randomized controlled trials were included. Meta-analysis revealed that exercise therapy significantly increased the peak knee flexion angle (SMD, 0.51 [95% CI, 0.09 to 0.93]; P = .02) and hip extension moment (SMD, 0.39 [95% CI, 0.02 to 0.76]; P = .004) and reduced the peak knee valgus angle (SMD, −2.47 [95% CI, −3.54 to −1.41]; P < .001) compared with the control group. Moreover, the regulatory effect of exercise therapy on vertical ground-reaction force exhibited task dependency but had no significant influence on peak hip flexion angle (SMD, −0.34 [95% CI, −0.36 to 1.04]; P = .34), knee extension moment (SMD, −0.01 [95% CI, −0.33 to 0.35]; P = .95), or knee valgus moment (SMD, −0.32 [95% CI, −0.81 to 0.16]; P = .19). Conclusion: Our review demonstrated that exercise therapy can improve lower-limb biomechanical characteristics after ACLR. However, existing exercise therapy cannot fully restore biomechanical deficits in those who underwent ACLR. Further research is required to explore the effectiveness of targeted long-term training interventions. This study has been registered in the International Prospective Register of Systematic Reviews (PROSPERO; registration No. CRD420251066193).