The Role of Lubrication in Biomechanical Joints

This paper attempts to present an overall picture of the various biomechanics problems in a synovial joint. Of particular interest is the lubrication mechanism between the articulating surfaces. A survey of pertinent information in regards to the constituents, i.e., the cartilage and the synovial fluid, indicates the possible types of constitutive equations which one must use to approximate their mechanical behavior. The approach is phenomenological. Further, the results of some of the lubrication theory are applied to the system under consideration. Using realistic physiological limits upon the loading and the speed of operation, the results seem to indicate that the mode of lubrication is elastorheodynamic. This is a term which describes the theory of lubrication in which the deformation of the cartilage and the non-Newtonian nature of the synovial fluid are considered. Finally, a list of problems is proposed. Their solutions are invaluable in settling the question of the proper description of the mechanism of synovial joints. Presently, research is under way in attacking one of these problems.