Pressure Distribution Underneath the Human Foot

Abstract

Force platforms which measure the net ground reaction force under the foot have become a standard item of equipment in locomotion laboratories over the last decade. These devices have the major limitation that the instantaneous distribution of force or pressure can only be described by a single point — the center of pressure — which identifies the geometric centroid of the applied force distribution. This measure sometimes has very little relevance to the anatomy or pathology of the foot. This point is dramatized by the results of a simple experiment shown in figure 1. The subject walked over a force platform and a pressure distribution platform with and without a 1 cm diameter marble placed in the shoe underneath the first metatarsal head. This painful situation for the subject resulted in center of pressure patterns (fig 1a) which were virtually identical. The pressure patterns, however, revealed a small peak in the location of the marble coincident with the subject’s pain.