FRICTION AND WEAR CHANGES IN SYNOVIAL JOINTS

Synovial joints have complex and poorly understood friction and wear p roperties. The relative importance of synovial fluid and cartilage in terms of lubrication is still unclear. The friction and wear character istics of cartilage surface was investigated by sliding the orthopaedi c cartilage of an adult rat femur against a stainless steel prate. Tes ts were performed dry and with irrigation by synovial fluid or saline solution. Friction and wear of the cartilage were initially low but in creased in severity as a superficial lubricating layer was progressive ly removed by wear. Irrigation of the cartilage by synovial fluid redu ced friction to very low levels, but saline solution had no lubricatin g effect. Microscopic examination of worn cartilage surface showed tha t low friction coincided with limited damage to the cartilage surface. It has been concluded that the outer surface of orthopaedic cartilage is covered by a substance capable of providing lubrication for limite d periods when synovial fluid is unable to prevent contact between opp osing cartilage surfaces.