Mechanism of Boundary Lubrication and Wear of Frictionless Synovial Joint

The natural synovial joints have excellent lubricating ability to provide very low frictional resistance and high wear resistance during various activities of human being. Synovial fluid is having mainly constituents of glycoproteins and phospholipids. Albumin adsorbs over globulin by hydrophobic bonding after formation of globulin coating on hydrophilic cartilage surface and phosphatidylcholine adsorbs over hydrophilic surface of albumin by the formation of phospholipid bilayer. Different interface of adsorbed proteins and phospholipids layer produces very low shear stress and produces the synovial joint highly slippery and frictionless. Still, synovial joints are effected by Osteoarthritis due to degeneration of cartilage surface. Due to very very slippery boundary lubrication of synovial joint, abrasive and adhesive sliding wear of cartilage surface is not possible. Present study describes the damage mechanism of articular cartilage on the basis of asperity fatigue model. As knee joint bear much more load than that of hip joint during walking, knee joint is early effected in Osteoarthritis. As gradually, cartilage surface detoriates loosing ultimate strength and modulus of elasticity, wear rate increases with aging of human being. It indicates ultimate result of Osteoarthritis at old age. Keyword: Synovial joint, Boundary lubrication, Asperity fatigue wear, Osteoarthritis