We developed a dynamic measurement system for contact pressure distribution in human joints using a thin carbon-particle-impregnated rubber pressure sensor particularly designed for this application together with a simple circuit. The electric resistance in the thin rubber correlates well with the amount of pressure applied. The sensors are flexible and have the ability to adapt to concave surfaces, sufficiently low hysteresis, high test-retest reliability and sufficient endurability. The indentation tests of a thick elastic layer by cylindrical and spherical punches were carried out to make a comparison of the contact pressure distributions measured with those due to a three-dimensional theory of elasticity and to estimate reliability of the sensing system. This system was applied to the patellofemoral joint of human cadaver knees in order to study kinematics of the joint. The results obtained show that the mean pressure on the patella with any flexion angles and the tension in the quadriceps are constant.
