The lubricating activity of human synovial fluids

Abstract

The lubricating abilities of human synovial fluids were measured using a rotating cartilage-on-glass apparatus. A total of 247 human fluids were lubricationtested. Of these, 20 of the 180 knee fluids from patients with degenerativehaumatic joint disease lubricated less well than normal bovine synovial fluid. The remainder of the fluids from the knee and other joints were equivalent to normal bovine synovial fluid in their lubricating properties. The concentrations of hyaluronic acid, protein, and sialic acid and the relative viscosity of 117 human fluid samples were determined, but no relationships between the gross composition and the lubricating abilities were apparent.Several types of friction measuring devices have been used to measure the lubricating ability of synovial fluids, and a number of mechanisms by which synovial fluid lubricates articular cartilage have been suggested (1-3). Possibly a combination of mechanisms, working in concert, enables synovial fluid to function as a cartilage lubricant. The extent to which failure of one or more of these mechanisms may limit the lubricating functions of synovial fluid, and contribute to the occurrence of joint diseases, is not known.Our approach to the study of cartilage lubrication has been to fractionate synovial fluid by biochemical procedures and to determine which components are able to act as lubricants in a friction measuring device. In initial studies (4,5), an oscillating cartilageon-cartilage test system was used, and we were able to determine that a purified synovial fluid glycoprotein fraction was able to lubricate articular cartilage. More recently, a simplified rotating cartilage-on-glass friction measuring apparatus was used ( 6 ) . Solutions containing a single detectable glycoprotein (lubricin) (7) at concentrations as low as 30 pgiml had lubricating properties that were similar, if not identical, to those of whole synovial fluid. These results showed that lubricin was an extremely efficient lubricant for articular cartilage and indicated that lubricin was the component that endows synovial fluid with its boundary lubricating properties (8,9).The prior studies were all performed on bovine metacarpophalangeal synovial fluids. The present experiments were undertaken to obtain information about the lubricating ability of human synovial fluids by performing tests on pathologic samples using the rotating cartilage-on-glass test system. PATIENTS AND METHODSSynovial fluids. Human synovial fluids were obtained from patients seen at the Arthritis Unit at the Massachusetts General Hospital. Following the completion of clinical laboratory tests, the samples were stored at 4°C for variable lengths of time (1-4 days). The samples were clarified by

Experimental verification of the role of interstitial fluid pressurization in cartilage lubrication

“…In recent years there has been a revived interest in the role of articular cartilage boundary lubricants such as phospholipids [14] or lubricin [43,44] and related glycoproteins such as superficial zone protein [11,16,38,42]. Many of the studies that have investigated the influence of these boundary lubricants on cartilage friction have not accounted for the role of interstitial fluid pressurization, perhaps attributing the low frictional coefficient of cartilage entirely to these lubricants.…”

Homology of lubricin and superficial zone protein (SZP): Products of megakaryocyte stimulating factor (MSF) gene expression by human synovial fibroblasts and articular chondrocytes localized to chromosome 1q25

“…Lubricin, a mucinous glycoprotein with an observed molecular weight of 337.5 kDa, is the factor responsible for boundary lubication of diarthrodial joints [33,24]. Lubricin is roughly 50% (w/w) glycosylated [25] with 0-linked p-( 1-3)-Gal-GalNAc oligosaccharides capped with NeuAc non-uniformly and appears to be a semirigid rod shaped structure of roughly 800 amino acids [26].…”

“…Lubricin was originally found to be the one synovial fluid component capable of lubricating a bearing of rabbit phalanx cartilage revolving on a plate of glass [24]. Lubricin lubricated the non-biologic test surfaces of latex and glass with the effectiveness of unfractionated synovial fluid [lo].…”

The submicroscopic structure of caprine articular cartilage in ontogeny

“…This layer, thick in the prenatal period, grows thinner with age. It is responsible for smooth gliding movement of articular surfaces which are often subject to enormous loads (Chappuis et al 1983;Swann et al 1984;Hills 1989). Lubricating substance, which is produced by synovialocytes, reduces the coefficent 9ffriction to 0.01.…”