Lubrication properties of post-injury synovial fluid: The relationship between friction, wear and its biochemical contents

The articular cartilage and synovial fluid (SF) function synergistically to maintain a low-friction and wear-resistant environment in joint articulation. Although interrelated in nature, the relationship between friction and wear is yet to be clearly elucidated. Wear was shown to be modulated by the mechanical strength of cartilage and the lubricant. Friction was shown to depend on the lubricant and the biochemical constituents of SF. In post-injury SF, the coefficient of friction was found to be higher than in normal SF, and was postulated to be due to alteration in the biochemical constituents in SF. However, it is uncertain if similar trend follows in wear.; The objectives of this study were to determine the wear-protective properties of normal and post-injury SF, and the relationship between friction and wear with SF lubricant. Results showed that wear did not vary with SF, and there was weak linear correlation between friction and wear. Another objective was to determine the relationship between protein, hyaluronan and phospholipid in SF, with friction and wear. Linear correlations were stronger between these molecules with friction, but weak with wear.; Collectively, results suggested that there was no clear relationship between friction and wear via this particular wear test, in which only late-stage wear was measured. Additionally, the stronger relationship between friction and SF molecules as compared to wear and SF molecules suggested that the modulators of wear are not limited to SF molecules. Therefore, future studies are required to further elucidate the modulators and the progression of wear in articular cartilage.