Passive and active mechanical properties of the human knee joint in abduction-adduction

Biomechanical properties about the abduction-adduction axis of the human knee joint were studied in vivo, using a newly developed joint driving device. Abduction-adduction torque-angle relationship reflecting knee abduction-adduction laxity and stiffness was determined quasi-statically at full extension for both relaxed knee and for knees actively producing abduction-adduction moment. Knee joint stiffness, viscosity and limb inertia about the abduction-adduction axis were estimated through a dynamic experiment for both passive and actively contracting knees. It was found that human knees have significant abduction-adduction strength, which can be used to reduce abduction-adduction laxity and increase stiffness and is potentially significant in maintaining joint stability and control joint motion. The knee joint showed much higher stiffness and viscosity in abduction-adduction than in flexion-extension for the same level of background muscle torque.