Contact patterns at the tarsal joints

Objective. To determine the contact patterns at the tarsal joints under two levels of loading (150 and 600 N) with the foot in the neutral position, plantarflexion, dorsiflexion, inversion and eversion. Design. In vitro measurements quantifying the size, location and patterns of contact. Background. Several methods have been employed to study contact areas and patterns in joints such as the hip and knee; in contrast there is limited data on the joints of the foot. Methods. Contact areas and patterns were determined by injecting coloured dyes, one for each level of loading, into the joint spaces in 23 pairs of feet: three pairs in the neutral position, five pairs in each of plantarflexion and dorsiflexion, and ten pairs in inversion (right foot) and eversion (left foot). Results. Contact area maps were constructed for the ankle, subtalar, talonavicular, calcaneocuboid, cuneonavicular and the intercuneiform joints. Quantification of the surface areas was performed using a digitizer. The extent of the changes in contact area appeared to be related to the mobility of the joints under consideration, with the greatest changes in contact pattern and area being associated with the most mobile joints. Conclusion. The small change in absolute contact area with increased loading reflects the role of the foot, in providing a stable support for the body during gait.