Ankle dislocations occur when significant force applied to the joint results in loss of opposition of the articular surfaces. Because of the large amount of force required and the inherent stability of the joint, dislocation rarely is seen without associated fracture. The ankle joint is designed for a balance of stability and flexibility, particularly the former.
Joint stability is provided by close articulation of the talus with the tibia and fibula.
The mortise design further enhances the stability of the configuration. The talus is trapezoidal in shape, with the greater width anteriorly. As the joint moves into plantar flexion, the talus becomes narrower, resulting in a decrease in stability. During normal walking, the ankle joint bears 3-5 times the body weight. This factor increases severalfold during running and jumping activities.