[The role of protein and hyaluronic acid in the synovial fluid in animal joint lubrication].

The purpose of this investigation was to study the role of protein and hyaluronic acid of synovial fluid in the animal joint lubrication. The D-fraction (0.2 micron up to 0.8 micron) from the bovine synovial fluid showed the lowest friction coefficient and contained about 20% protein and 70% hyaluronic acid of the synovial fluid. Protein but not hyaluronic acid of this fraction had lubricating ability, and the protein but not hyaluronic acid could support the lubricating film thickness. By electron microscopic observation hyaluronic acid was 2,000A-5,000A formless mass and the protein complex that had lubricating ability was 200A-300A spherical particle. Through these results I presume that hyaluronic acid enclose the spherical protein particles in its network like a cage of the roller-bearing and the particles can rotate freely like rolling elements of the roller-bearing. It was suggested that the roller-bearing mechanism was performed along with elastohydrodynamic lubrication in animal joint.