Abstract
In healthy joints, the cartilage surface coated with phospholipid multi-bilayers is governed by the lamellar-repulsive hydration mechanism. The phospholipid bilayers of biological surface are investigated by friction testing, while surface degradation is controlled by wettability. This paper proposes the presence of cartilage surfaces that are negatively charged results in highly efficient lubrication in natural joints. At pH similar to 7.4, the mechanism of lamellar-repulsion between contacting cartilage surfaces is supported by charged macromolecules of synovial fluid and phospholipid lamellar phases. It was proven experimentally that phospholipid (PLs) bilayers with lamellar structure can act as an effective solid lubricant in friction and wear under biological test conditions.