There are clearly two separate systems in animal joints which require lubrication; the cartilage on cartilage system and the soft tissue (synovial membrane on itself or on cartilage) system. These 2 systems are both subject to boundary lubrication but with two chemically separate and distinct fractions of the synovial fluid. The cartilage on cartilage lubricating fraction is glyco-peptide which has a molecular weight of about 250,000 and consists of approximately equal amounts of peptide and carbohydrate constituent. The soft tissue system lubricating fraction is high molecular weight hyaluronate. This latter lubricating mechanism is extremely molecular weight sensitive. Investigations will be performed to delineate the origin and molecular interaction of these lubricating fractions with the articulating surfaces of the joint and relate these to the normal and diseased states.