[Biomechanics of the ankle joint--injury mechanisms]

The complex mechanics of the ankle joint complex depends highly on the integrity of the ankle ligaments. An incomplete restoration of the antero-fibular ligament after trauma may result in a mechanical dissociation of the talus from the ankle mortise. The force that is needed to induce a non-physiological movement of the foot is determined by the individual configuration of the bony and articular structures of the hindfoot. A pes cavus is less protected to suffer of an ankle sprain than a flatfoot. As the leverarm of the peroneal muscles decreases with increasing plantarflexion of the foot, the active protection to resist against a supination stress decreases with plantarflexion. These findings have significant implications for the practice. First of all an adequate treatment of any ankle sprain is necessary to restore the mechanical interplay of the ankle joint complex. Ankle orthoses should protect the foot against supination stress and excessive plantarflexion. The prevention of ankle injury may be significantly improved by recognition of the individual mechanical disposition.