In a healthy joint, a thick, slippery substance called synovial fluid provides lubrication, allowing bones to glide against one another. It is especially important in preventing wear and tear by keeping the bones slightly apart and acting as a shock absorber. In individuals with osteoarthritis, an important substance in synovial fluid, known as hyaluronic acid, breaks down. Reduction of hyaluronic acid can lead to joint pain and stiffness associated with osteoarthritis.