Compression tests on plugs of bovine articular cartilage and of subchondral bone demonstrated that both are capable of deforming under pressure and thus attenuating peak dynamic forces applied to the plugs. Although cancellous bone is approximately ten times stiffer than articular cartilage per unit of thickness, subchondral bone in vivo is considerably thicker and would, therefore, seem capable of contributing to dynamic force attenuation as much as the cartilage does or more. Under physiological loads and loading rates, a film of synovial fluid on the cartilage added nothing to the ability of cartilage plugs to attenuate peak dynamic force; however, at very low load rates cartilage plugs coated with synovial fluid were consistently stiffer than specimens coated with veronate buffer. It is highly likely, from the evidence presented, that alterations in the quality of the subchondral bone could have a profound effect on the ability of a subchondral bone-articular cartilage system to withstand compressive dynamic forces.