[Intra-articular and plantar pressure distribution of the ankle joint complex in relation to foot position]

Ankle injuries are often followed by degenerative changes in the hindfoot joints. Knowledge about the pressure distribution of the intact ankle joint may help to understand the mechanisms leading to cartilage damage. Therefore, we determined the intraarticular and plantar pressure distribution of the ankle joint complex and the Chopart joints with varying foot positions. 12 human lower leg specimens were axially loaded in a foot-loading simulator with full body weight (600 N). A capacitive pressure distribution platform was used to determine plantar pressure patterns. The intraarticular loading situation was measured with Fuji Prescale film. 3 different foot positions (neutral, 10 degrees dorsiflexion, 10 degrees plantarflexion) were investigated. Dorsiflexion led to an increase of the intraarticular contact area, force and mean pressure in the hindfoot. Plantarflexion instead increased loading in the Chopart joints. In the plantar pressure distribution force and peak pressure under the hindfoot increased with dorsiflexion. With plantarflexion area, force and peak pressure under mid- and forefoot increased. With our study we could demonstrate that the loading situation of the ankle joint complex is significantly influenced by the foot position. These findings may help to understand the development and localisation of arthritic changes due to posttraumatic changes of the joint loading characteristics.