The load-bearing area in the knee joint

Measurements were made of the location and size of the contact areas in cadaver knee joints, for a load of 150 Kgf applied for 5 sec down the long axis of the tibia. Results were obtained from a total of 4 knees, considering flexion angles from 0 to 120°. The methods used were to measure directly from castings of the joint cavity; and to calculate from measurements of radii of curvature and joint deflection. Average contact areas for lateral and medial condyles were 1·4 and 1·8 cm2 respectively. Areas for the medial condyle were greater than for the lateral condyle and also the areas diminished as flexion angle increased. The implications of the results to contact stresses, joint lubrication and ‘condylar replacement’ knee prosthesis design were discussed.