Viscoelastic properties of hyaluronic acid and biological lubrication
Balazs, E.A.
University of Michigan Medical Center Journal 1968: 255-259
1968
ISSN/ISBN: 0041-9826 PMID: 5728249 Document Number: 6000
The biological lubrication in a broad sense deals with the friction between two load-bearing surfaces, and with the protection of these surfaces against mechanical stress. There are three types of bearing surfaces to consider. The cartilage surface in joints, the tightly packed, parallel running collagen bundles in the tendons, and the membranes of two-dimensional networks of collagen fibers in the subcutaneous and intramuscular connective tissue, In all three cases, the viscoelastic tissue is interposed between two load-bearing solid surfaces. According to the latest theory of joint lubrication,lo the low friction between the surfaces is maintained by a mechanism called elastohydrodynamic action. In this mechanism, porous bearing surfaces are protected from direct contact by a fluid film having a highly effective resistance to distortion under load. The emphasis is on the porosity of the surface layer, which permits the penetration of macromolecular components of the fluid film and the flow of water in and out of the bearing surface itself. The protection of the bearing surfaces, and the cells embedded in them, is provided by the viscoelastic property of the fluid and the matrix of the solid surface. The two-compartment intracellular matrix system of the cartilage bearings, tendon bearings and membranous fascia bearings, function under various conditions of mechanical loads, shocks, and vibration; they all perform the triple function of lubrication, shock absorption and vibration isolation. It must be emphasized that these three functions are inseparable and inherent in the general structural features of these biosystems. The intention of our investigations was to bring into focus the viscoelastic properties of the liquid that forms the fluid film between the bearing surfaces and that also penetrates the surfaces, thereby providing the main viscoelastic component of the solid matrix itself. In conclusion, we suggest that the biological lubrication, shock absorption and vibration isolation are inseparable functions of the biological bearings of all kinds. Furthermore, we propose that the viscoelastic properties of the hyaluronic acid in the fluid phase and the solid intracellular matrix provide the fundamental mechanochemical component for the proper function of these biosystems.
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