Studies already performed have shown that high molecular weight glycoprotein (LGP-I) is responsible for the boundary lubrication of articular cartilage by synovial fluid. The function of LGP-I, however, may be facilitated by a second glycoprotein (LGP-II) also present in synovial fluid and which is very similar to another glycoprotein present in the surface layers of the articular cartilage. Chemical experiments will be performed to determine the detailed structure of the glycoproteins to elucidate their mechanisms of action at the articular cartilage surface. The presence of a fluid squeeze film contributed both by the synovial fluid and also the interstitial cartilage fluid, however, is the major mechanism responsible for the lubrication of the tissue. This mechanism is dependent upon the macromolecular organization if the extracellular matrix constituents (proteoglycans, glycoproteins, hyaluronic acid and collagen) and it is planned to continue the study of the structure and interactions between these constituents to determine the relationships that exist between structure of the tissue and its function in joint lubrication and resistance to wear. These studies will involve in vitro experiments with scarified and chemically modified cartilage of bovine joints and the osteoarthritic joints of dysplastic dogs. The lubrication and wear properties of these joints and the ability to improve function by retarding wear will be determined. Extensive chemical studies will be carried out to obtain purified cartilage constituents which can then be used to produce specific antisera for use in the tissue localization of the matrix macromolecules both in the normal, scarified and osteoarthritic cartilage. The results of these experiments will be compared with data obtained by chemical analysis of human osteoarthritic cartilage obtained at surgery and autopsy.