INVESTIGATION INTO THE EFFECTS OF PROTEINS AND LIPIDS ON THE FRICTIONAL-PROPERTIES OF ARTICULAR-CARTILAGE

The aim of this study was to investigate the effects of the proteins a nd the lipids on the frictional properties of articular cartilage in t he mixed and boundary lubricating regimes. Bovine articular cartilage that had been treated to remove the lipids, and cartilage that had bee n treated to remove the proteins, from the surface layer were studied in order to investigate differences in their lubricating abilities. Te sts were carried out on a sliding friction rig under contact pressures of 0.5 and 4 MPa. The results of the friction tests carried out under the 4 MPa contact pressure showed a slight increase in friction coeff icient for both the lipid and the protein deficient cartilage when com pared with the control cartilage. These differences were more apparent at the shorter loading times but none of the differences were found t o be statistically significant. The tests at the lower contact pressur e of 0.5 MPa showed that removing the lipids by washing the surface wi th detergent increased the friction coefficient at the shorter loading times but had no effect at the longer loading times. Digesting the ca rtilage with trypsin to remove the proteins from the surface layer had no effect on the friction coefficient at the shorter loading times bu t reduced the friction coefficient at the longer loading times. Both t hese results were confirmed with specimens that had both the lipids an d the proteins removed from the surface layer. (C) 1998 Published by E lsevier Science Ltd. All rights reserved.