Loads on the Knee Joint Ligaments during Stair Climbing

Background. Stair climbing is often performed by people in daily life and requires considerable energy and muscle effort. This task has been widely described in the literature, but the role of the knee joint ligaments has not been sufficiently investigated. This could be relevant for planning ligament reconstruction surgery, for providing suggestions to subjects with partial ligament injuries, and for identifying compensatory strategies for reducing ligament loads. Methods. A dynamic musculoskeletal model was used to analyse the relationship between ligament loads and muscle forces during stair climbing. Results. The most loaded ligaments were the posterior cruciate ligament and the deep fibres of the medial collateral ligament, particularly during the mid-swing phase, where the knee was maximally flexed and the hamstring muscles contracted. The anterior cruciate ligament was recruited during the stance phase to compensate for the anteriorly-directed force applied to the tibia by the vasti muscles; the collateral ligaments stabilized the knee joint during the swing phase. The tibiofemoral contact force, resulting from all external and internal forces applied to the knee, was in good agreement with data provided in the literature. Conclusions. This study represents a forward step in the knowledge of ligament loads during stair climbing, which could be useful for providing informed recommendations to subjects with ligament injuries.