Abstract
Articular cartilage, comprising the sliding surfaces of diarthrodial joint, produces very low friction coefficients and has excellent wear properties. Understanding the lubrication of diarthrodial joints has been an important objective in the field of biomechanics since the early part of this century. But not until the 60s has the role of cartilage in joint lubrication been specifically investigated in parallel with the development of cartilage mechanics. The role of cartilage in joint lubrication includes the time, velocity, and load dependence of cartilage friction (McCutchen, 1962; Malcom 1967; Wright and Dowson, 1967); furthermore, in our own recent investigations, it has been observed that cartilage exhibits a very significant normal stress effect under steady frictional shear (Wang and Ateshian, 1995). Furthermore, it was observed that the normal stress effect persists even after removal of the surface zone (Wang and Ateshian, 1996), demonstrating that this effect is attributable to intrinsic properties of the cartilage rather than a boundary lubricant adsorbed to the surface. Following these studies, it was hypothesized that the normal stress effect is related to the proteoglycans present in the tissue, since Theological studies of proteoglycan solutions (Zhu et al., 1991) have been shown to exhibit a normal stress under steady shear; hence it is possible that proteoglycans in the tissue matrix impart to the interstitial fluid a non-Newtonian behavior which is responsible for the observed normal stresses. Therefore, the goal of this study was to determine the effect of specific removal of glycosaminoglycan chains on the normal stress.
