Lubrication Property of Hydrogel Layer on Articular Cartilage Surface

The purpose of this research was to investigate the lubrication property of the hydrogel layer on cartilage surface. A Custom-made friction testing machine was used to clarify lubrication property of articular cartilage. The specimens were taken from the patella groove of porcine knee joint. Two kinds of superficial condition were evaluated. In the intact group, the cartilage surface was preserved. In the wiped group, the cartilage surface was gently wiped with Kim Wipe. The start-up friction coefficient of the intact group was lower than that of the wiped group for all load condition, and it depended on the sliding speed for the low-load condition. Stribeck curve showed that start-up friction coefficient of the intact group was kept low and that of the wiped group is higher than that of the intact group for all conditions. The Lift-up test was divided into two intervals of 30minutes. Between these intervals, the specimen was unloaded and separated from stainless plate. The time of unloading was 1minute. Friction coefficient after 30minutes and 61minutes were measured. In the case of the intact group, the difference between friction coefficient at 30minutes and that at 61minutes increased with increasing load. In the case of the wiped group, friction coefficient at 30minutes was almost same as that of 61minutes. When proteoglycan attached to the stainless plate increased, friction coefficient of the intact group became higher and closer to that of the wiped group. In conclusion, the existence of the hydrogel layer on the cartilage surface contributed for low friction.