The biomechanical study of the subsequent injury of an ACL deficient knee

Meniscus and ligament ruptures are common in anterior cruciate ligament (ACL) deficient knee. The mechanism of injuries is still unclear, and was mainly inferred from ex vivo experiments and clinical studies. In this study, a three dimensional finite element model of knee joint was reconstructed from magnetic resonance images. The geometry data of the knee from literature was used to validate the model. Tibial displacement and in situ force in ACL in response to the anterior tibial loads were calculated and coincided with the published experimental data. The simulations of the models with and without ACL were performed under anterior tibial loads and axial tibial loads at 0° and 30° flexion. Our results suggest that ACL deficiency could lead to abnormal stress distribution: the stress near the posterior insertion of the medial meniscus increased significantly; the changes of the stress in the lateral meniscus, posterior cruciate ligament and collateral ligaments depended on the loads and the flexion angles. This study may help to explain the higher subsequent injury rate of ACL-deficient knee, and to predict the injury risk positions in the joint. Furthermore, this model could shed some light on the mechanism of ACL injuries and the treatments.