Progressive Bilateral Alterations in Gait Biomechanics Within 2 Years After Anterior Cruciate Ligament Reconstruction

Background: Bilateral gait biomechanics change over time after anterior cruciate ligament reconstruction (ACLR) and have been suggested to contribute to the development of osteoarthritis. However, few studies have investigated the longitudinal changes in bilateral gait biomechanics in the same cohort within 24 months after ACLR. Purpose: To evaluate the longitudinal changes in bilateral gait biomechanics compared with the healthy control cohort within 24 months after ACLR. Study Design: Controlled laboratory study. Methods: A total of 24 patients who underwent primary unilateral ACLR surgery with autologous hamstring tendon grafts and 24 matched healthy participants were included. Also, 3-dimensional knee gait and ground-reaction forces (GRF) information were collected at 3, 6, 12, and 24 months after ACLR. Linear mixed-effects models were used to assess the influence of time and limb in ACLR participants and their interaction effect on each variable of interest. Two-way analysis of variance was used to compare intergroup and interleg dependent variables. Results: Three months after ACLR, most biomechanical parameters of the operated limb (peak knee extension angle pKEA; peak knee extension moment pKEM; peak knee flexion moment pKFM; and vertical ground-reaction force vGRF) were lower than both the contralateral limb and healthy controls, and gradually increased over time. By 24 months postoperation, the pKEA and the pKEM returned to normal levels. The operated limb showed significantly reduced pKEA and pKEM compared with contralateral and control groups at 3 and 6 months (all P ≤. 001), with no clinically meaningful differences at 12 and 24 months. pKFM analysis revealed significant between-group effects (ACLR group vs control group) without limb or interaction effects from 3 to 24 months, indicating bilateral compensatory reduction. Regarding vGRF, GRFₚeak1 demonstrated bilateral compensatory reduction at 3 months (resolved by 6 months), while GRFₚeak2 showed operated limb reduction at 3 months progressing to bilateral compensation at 6 months (resolved at 12 months). Notably, both vGRF parameters exhibited bilateral compensatory reductions again at 24 months postoperation. Conclusion: Three months after ACLR, sagittal plane biomechanical parameters of the operated knee (pKEA, pKFM, pKEM) and GRFₚeak1/2 were significantly lower than those of controls, except pKFA, which showed no intergroup difference. Longitudinal analysis revealed partial recovery patterns: GRFₚeak1 was normalized by 6 months, while GRFₚeak2, pKEA, and pKEM reached control levels by 12 months. However, a secondary decline emerged at 24 months, with GRFₚeak1/2 values again significantly lower than those of the controls, and the pKFM remained persistently lower than that of the controls throughout the 24-month follow-up. Early postoperative gait retraining and neuromuscular control training are recommended, with sustained interventions maintained for at least 24 months. Clinical Relevance: Bilateral gait retraining and neuromuscular control training are recommended as early as possible and should be maintained for at least 24 months after surgery.