Three-dimensional kinematics of the rearfoot during the stance phase of walking in normal young adult males.

Three-dimensional video analysis was used to quantify three-dimensional motion of the rearfoot in 14 normal young adult males during the stance phase of walking. A stringent calibration procedure enabled standardization of the neutral position of the rearfoot. Surface markers were placed on the calcaneus and lower tibia, and a joint coordinate system was used to determine the relative displacement between the calcaneus and lower leg as representative of rearfoot motion. Confirmation was made of the assumption of a mechanical coupling between the rearfoot displacements of abduction/adduction and eversion/inversion. However, there were several findings which contrasted with commonly held assumptions. For example, the rearfoot was found to evert gradually, rather than rapidly, from heel contact to just prior to heel rise. Also the conventional descriptions of the composite movements of pronation and supination were not applicable to rearfoot movement in this study, and it was therefore concluded that pronation and supination are not valid descriptors of three-dimensional rearfoot motion during the stance phase of walking.