Interlimb differences in knee joint loading and stress distribution following anterior cruciate ligament...

Despite anterior cruciate ligament reconstruction (ACLR), many patients exhibit persistent interlimb biomechanical differences during high-demand tasks like stair descent, which may contribute to post-traumatic osteoarthritis. However, it remains unclear how these movement adaptations translate into altered internal tissue loading within the knee joint.

This study therefore integrated motion capture, surface electromyography (EMG), musculoskeletal modeling, and subject-specific finite element (FE) analysis in 34 individuals following unilateral ACLR participated in this study. Joint kinematics and kinetics derived from experimental data were used to drive an MRI-based FE model, with tibiofemoral motion validated via dual fluoroscopic imaging system (DFIS).

Compared with the contralateral limb, the ACLR limb exhibited reduced quadriceps activation, increased hamstring activity, lower knee flexion angles (p = 0.023), and significantly reduced knee extension moments (p < 0.001) during stair descent. Ankle-level compensation included reduced plantarflexion moments (p < 0.001). Finite element analysis revealed consistently higher von Mises stresses in the ACLR limb, particularly in the medial tibial cartilage, posterior menisci, and posterior cruciate ligament, with peak stresses 10-50% greater than the contralateral limb.

Persistent neuromuscular and interlimb biomechanical differences six months after ACLR translate into altered internal knee load distribution during stair descent. Reduced knee extension moments and compensatory strategies shift load toward secondary stabilizing structures, potentially increasing the risk of cartilage degeneration. These findings provide a mechanical basis for understanding altered load distribution following ACL reconstruction and offer valuable insights for predicting long-term joint degeneration risk.