Osteoarthritis is a common joint disorder in humans. Although intra-articular injection of hyaluronic acid (HA) is in widespread clinical use, there are limited data on the effect of HA on degenerated cartilage. When bovine articular cartilage is degraded with interleukin-1, HA penetrates the cartilage and accumulates in the pericellular matrix of chondrocytes. HA also enhances proteoglycan synthesis that has been reduced by interleukin-1. Thus HA seems to have anabolic effects on degraded cartilage.