Osteoarthritis (IMAGE) American Chemical Society Caption This illustration shows a joint with severe osteoarthritis. Osteoarthritis wears away the cartilage at the ends of the bones. Spurs then grow out from the edge of the bone and synovial fluid increases. This may cause the joint to feel stiff and sore. Credit Credit: National Institute of Arthritis and Musculoskeletal and Skin Diseases. Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.