The mathematical representation of the articular surfaces of anatomical joints can be obtained in a piecewise continuous fashion using parametric surface patches. The relative position of the anatomical bodies containing the articular surfaces can be measured with an instrumented spatial linkage. By combining the relative position data with the mathematical representations, the approximate area of contact between the articular surfaces can be determined. In this paper, the procedure for combining motion data with surface contour data is described, and in-vivo areas of contact in the canine shoulder for a normal test subject are presented.