The Frictional Behavior of Human Synovial Joints—Part I: Natural Joints

Abstract

Some theoretical consideration has been given to the use of pendulum machines when used to examine the frictional properties of human joints by incorporating them as fulcra. As a result, a new type of pendulum machine has been built which incorporates the facility to apply sudden loads to the joint on starting the swinging motion, and also the ability to measure directly the frictional torque experienced by the joint. The results obtained from natural hip joints (reported in Part I) indicate the presence of squeeze film lubrication under conditions of sudden loading. In addition, a self-generated fluid film process was observed at low loads whilst at high loads boundary lubrication appeared to be important. Artificial joints (Part II) are shown to exhibit similar lubrication properties to the natural joints but with a higher absolute value of friction. The metal on plastic type of joint is shown to exhibit a creeplike phenomenon which recovers with time.