Osteoarthritis is a disease of the entire joint, involving the cartilage, joint lining, ligaments, and bone. The most common symptoms are joint pain and stiffness. A symptom of osteoarthritis differs depending on which joints are affected and how severely they are affected. The most common symptoms are pain and stiffness. Affected joints and muscles may get swollen, especially after extensive activity. These symptoms tend to increase over time rather than show up suddenly.