Paper 1: Physiological Lubrication

Abstract
Physiological lubrication differs from normal engineering practice in the materials used, and in the type of service to which the bearings are subjected. These permit or require—it is dangerous to specify which—at least two mechanisms which are outside conventional engineering. The first is weeping, or self-pressurized hydrostatic lubrication. This occurs because the bearing material is microporous and easily deformed, and because the service is always intermittent. The second is a form of boundary lubrication which can support only very small unit loading. Unlike the boundary lubricants of industry which adsorb as close-packed layers upon the bearing surfaces, the synovial mucin molecules are inherently dilute, each extending through a large volume of solution, and any adsorbed layer is likely also to be dilute. Such a swollen layer should, nevertheless, be able to support small loadings, because any attempt to compress it will be resisted by a pressure which is, broadly, of osmotic origin.