No abstract

A method is described for determining the rate of mechanical expression and resorption of fluid from cartilage and for determining its composition. Human articular cartilage, unlike costal tissue, showed little change in its total or expressible fluid throughout life. The extruded material resembled synovial fluid except for its low protein content and viscosity. It is suggested that the expressed fluid was held osmotically in the ground substance.Es describite un methodo pro determinar le valor del mechanic expression e resorption de liquido ab cartilagine e pro observar su composition. Human cartilagine articular-per contrast0 con tissu costal-monstrava in le curso del vita pauc alteration in su total de exprimibile liquido. L e exprimite material resimilava liquido synovial, excepte que ill0 habeva un basse contento de proteina e un basse viscositate. Es proponite le these que le exprimite liquido esseva retenite osmoticamente in le substantia de base.T HAS BEEN surmised for many years that the percolation of interstitial I fluid attending use of joints is an important mechanism in the nutrition of articular cartilage. Changes in the thickness of the joint cartilage accompanying exercise have been reported,' and the suggestion made that these are caused by shifts of fluid into and out of the tissue. It also has been variously proposed that insufficient mechanical circulation of the fluid2 or excessive leaching out of the chondromucoproteins" by the fluid plays a role in the pathogenesis of osteoarthritis. Several recent studies have emphasized the interstitial fluid and its movement as principal elements in the lubrication4 and elastic properties" of joints. The present studies were carried out to provide information on the ability of fluid to move into and out of articular and non-articular cartilage, how this is affected by age, and also on the content and composition of the fluid.The following items were investigated:1. The rate of expression of fluid under static loading and subsequent re-2. The water content of articular and non-articular cartilage at various ages.sorption. F r o m the Section on Rheumatic Diseases, Lahoratorv of Experimental Pathology, National

The coefficient of friction of dog ankle joints measured in vitro was found to be greatly affected by certain enzymatic treatments of bovine synovial mucin. Testicular hyaluronidase had no effect on its lubricating action even though it abolished the viscosity. By contrast, tryptic digestion destroyed the ability of the mucin to lubricate without reducing the viscosity. These observations indicate that a protein moiety is an intrinsic component of the mucin molecule; and that, together with an only partly polymerized hyaluronate, it is responsible for the mucin's function as a lubricant. The protein may serve as a prosthetic group for adsorption of the mucin onto the surface of the cartilage. Sodium heparin inhibited lubrication by the mucin. In mucin‐free buffers, the pH and molarity of the lubricant bath altered both the friction and deformability of the cartilage. The change in friction was not consistently related to the change in deformability. The amphoteric effect of pH on the friction raises the possibility that electrostatic surface effects contribute to adhesive friction. Formalin made the cartilage rigid and increased the coefficient of friction. It did not, however, have much effect on the lubricating action of the mucin. A small number of pathological human synovial fluids were studied and found to lubricate as well or better than healthy bovine material.