A technique for the study of contact between visco-elastic bodies with special reference to the patello-femoral joint

Contact areas in synovial joints have been determined by several techniques, most of which required that the joint should be loaded for long periods in order to obtain records of the contact areas. The time dependent nature of the cartilage deformation can cause errors in the contact areas obtained by these techniques. A simple experiment is described which demonstrates a time dependent behaviour of the contact area between a cartilaginous surface when loaded against a flat glass plate, and the load maintained for a long period. A new technique for determining contact areas in synovial joints which is named the Controlled Cartilage Compression Casting Technique is described. It takes into account the time dependent nature of the cartilage deformation. This technique is further developed for obtaining the contact areas in the patello-femoral compartment of the knee joint. The apparatus used is described and preliminary results from two knees are presented.