Investigation of Effect of Hyaluronic Acid Containing Medicine on Frictional Behavior of Synovial Fluid

Abstract

Cartilage and synovial fluid ensure the smooth movement of natural joints to work with very little friction. However, the number of patients with joint diseases, which are usually related to cartilage destruction, constantly increases. Therefore, understanding the tribological behavior of synovial fluid is of great concern in order to reduce its degradation and maintain a reliable joint function. The purpose of this research is to provide insight into the frictional behavior of synovial fluid, focusing on its composition and especially hyaluronic acid (HA) content, velocity, and applied load on the joint. Forthis purpose, a pin-on-disc simulator was used. The tests were accomplished at three different movement velocities and under three loads of 30, 60, and 100N. During the tests, the lubricants were pure synovial fluid and synovial fluid with 10% and 20% of a traditional osteoporosis medicine, i.e. Cynogel. The test results showed that the friction strongly depends on the HA content of the lubricant. Studying the applied load effect on the friction coefficient, it was found that hyaluronic acid's rheological behavior could neutralize the medicine's effect under a light load at a slow speed. After adding Cynogel into the synovial fluid, the friction coefficient decreased under higher loads. The greatest changes were observed for the 20% combination, which led to about 20% and 30% improvement in the friction coefficient at high and medium velocities, respectively.