Progressive Alterations in Gait Biomechanical Symmetry within 2 Years Post-Anterior Cruciate Ligament Reconstruction

Background: Persistent gait asymmetries following anterior cruciate ligament reconstruction (ACLR) are linked to post-Traumatic osteoarthritis. Insufficient understanding of the characteristics of gait biomechanical symmetry changes after ACLR hinders the improvement of rehabilitation strategies and the development of new rehabilitation techniques. Purpose: To evaluate longitudinal changes in gait biomechanical symmetry over 24 months post-ACLR and compare these to healthy controls. Methods: A total of 20 patients after unilateral ACLR surgery for the first time and 20 matched healthy participants were included, and three-dimensional gait and ground reaction force were collected at 3, 6, 12, and 24 months after ACLR, respectively. The interleg differences in the peak knee flexion and extension of angle and moment (pKFA, pKFM, pKEA, pKEM), the first and the second peak knee adduction moment (pKAM1), and the limb symmetry indices in the first and the second peak of the vertical ground reaction force (vGRF1, vGRF2) were evaluated. Results: At 3 months post-ACLR, patients showed significant sagittal asymmetries (pKFA, pKEA, pKFM, pKEM; all P<0.05) and reduced vGRF symmetry. By 6 months, pKFA and pKFM normalized; vGRF1 and pKAM1 (initially lower) resolved by 6 and 12 months, respectively. The recovery of pKEA symmetry required 24 months, while pKEM asymmetry persisted after 24 months (P=0.04). vGRF2 normalized at 12 months, demonstrating differential recovery across biomechanical parameters. Conclusion: ACLR patients showed significant gait asymmetries, and those asymmetries reduced notably over time. 24 months after surgery, gait symmetry after ACLR recovered to the level of control subjects, except that the asymmetries of pKEM still existed. Prolonged terminal stance-phase asymmetries post-ACLR require phase-Targeted exoskeleton technologies to restore gait symmetry and joint health.