Anterior Cruciate Ligament: Anatomical and Biomechanical Principles

The anatomical and biomechanical properties of the anterior cruciate ligament (ACL) are critical to understand function and movement of the knee. The ACL begins to develop early in the gestational process and becomes a unique structure composed primarily of type I collagen with important biomechanical and proprioceptive functions. The structural, mechanical, and viscoelastic properties of the ACL are fundamental to the functional behavior of the ACL under loading conditions. Primarily, the ACL functions to resist anterior tibial translation while also providing rotatory stability to the knee. Although the anteromedial and posterolateral bundles have distinct anatomical properties and functions, they work together in a synergistic manner during knee movement. Alterations in knee kinematics occur in the setting of ACL injury and can lead to increased strain on other soft tissue structures such as the meniscus, while also changing tibiofemoral contact points and potentially contributing to the development of degenerative chondral changes of the knee.