THE ROLE OF SYNOVIAL-FLUID FILTRATION BY CARTILAGE IN LUBRICATION OF SYNOVIAL JOINTS .1. MIXTURE MODEL OF SYNOVIAL-FLUID

A mathematical model of lubrication of human synovial joints under squ eeze-film conditions is presented in this several-part paper. Squeeze- film action leads to a concentration of hyaluronic-acid-protein macrom olecular complex in the synovial fluid between the approaching cartila ge surfaces as a result of the diffusion of water and low molecular we ight substances through the cartilage surfaces or along the gap. Incre asing viscosity of synovial fluid delays the approach of these surface s and the formation of stable gels then protects cartilage, if sliding motion ensues, before fluid film lubrication is restored. In Part I o f the present paper synovial fluid is considered as a mixture of two i ncompressible fluids. The material parameters of this mixture of fluid s are found using previously published experimental results. Squeeze-f ilm analysis is carried out for the axially symmetric synovial film.