The Hydrodynamic Squeeze Film Lubrication of the Ankle Joint

Abstract

The main aim of the study presented in this paper is to determine the characteristics of synovial fluid film region by modeling the human ankle joint to obtain an analytical expression for the pressure distribution, load carrying capacity, coefficient of friction and reduction of synovial film thickness with time of approach. Thus in order to reach a comprehensive analysis of the human ankle joint lubrication, variable behavior of synovial fluid during different time of joint activities and the influences of articular cartilage has to be taken into account. The behavior of the synovial fluid has been assumed to be isothermal, shear thinning and non- Newtonian couple stress fluid. The model of ankle joint has been taken geometrically and kinematically as a partial porous journal bearing under the action of hydrodynamic squeeze film lubrication. Typical geometrical and physical values of the ankle joint were acquired from measured values reported in literature. The problem of ankle joint lubrication has been solved numerically for various couple stress fluid parameters together with effect of varying the porosity of the articular cartilage. It has been shown , in the presence of porous articular cartilage, and by assuming the synovial fluid to be a non- Newtonian shear thinning couple stress fluid that the , pressure distribution, load carrying capacity, synovial film thickness with time of approach increased and a reduction coefficient of friction in the hydrodynamic squeeze action in the ankle joint resulted.