Multiscale analysis of the tribological role of the molecular assemblies of synovial fluid. Case of a healthy joint and implants

The aim of this work is to identify the coupled role of the biological components of synovial fluid in the remarkable tribological operation of a healthy natural joint, as well as in the friction of steel and polythene implants. It uses a realistic ex vivo model capable of reproducing the mechanical and physicochemical characteristics of the entire tribological triplet of the joint, whether healthy or implanted. It particularly focuses on the lipidic bilayers and vesicle structures associated with synovial fluid. The analysis of the friction measurements and fluorescence microscopy images confirm the role of lipidic bilayers in maintaining a very low friction coefficient. In addition, we observe that the substitute cartilage favours the formation and maintenance of these bilayers, which is not the case of implant materials. (C) 2007 Elsevier Ltd. All rights reserved.