ACL (anterior cruciate ligament) injuries of the knee joint alter biomechanics and may cause abnormal loading conditions that place patients at a higher risk of developing osteoarthritis (OA). There are multiple types of ACL reconstruction (ACLR), but all types aim to restore anterior tibial translation and internal tibial rotation following surgery. Analyzing knee joint contact loads provide insight into the loading conditions following ACLR that may contribute to the long-term development of OA. Ten ACLR subjects, who underwent the same reconstruction, performed gait and cycling experiments while kinematic and kinetic data were collected. Inverse dynamic analyses were performed on processed data using OpenSim to calculate reconstructed and contralateral knee joint contact loads which were then compared between gait and cycling at both moderate and high resistances.

Significant differences were found between gait and cycling at either resistance for tibiofemoral (TF) compressive, anterior shear, lateral shear forces, and internal abduction and internal rotation moments for both ACLR and contralateral knees. Anterior shear force was largest for cycling at a high resistance, however, since the ACL provides a posterior restoring force and is more engaged at low flexion angles, adjusting for flexion angles when measuring AP shear forces should be considered. Overall, the calculated loading conditions suggest cycling provided better joint stability by limiting anterior tibial translation and internal tibial rotation compared to gait. The results suggest cycling is a better rehabilitation exercise to promote graft healing and limit abnormal loading conditions that increase the risk of developing OA.