Physical conditions or diseases can cause knee pain. These include: osteoarthritis: pain, inflammation, and joint destruction caused by degeneration and deterioration of the joint tendinitis: pain in the front of the knee that is made worse when climbing, taking stairs, or walking up an incline bursitis: inflammation caused by repeated overuse or injury of the knee chondromalacia patella: damaged cartilage under the kneecap gout: arthritis caused by the buildup of uric acid Baker’s cyst: a buildup of synovial fluid (fluid that lubricates the joint) behind the knee rheumatoid arthritis (RA): a chronic autoimmune inflammatory disorder that causes painful swelling and can eventually cause joint deformity and bone erosion dislocation: dislocation of the kneecap most often the result of trauma meniscus tear: a rupture in one or more of the cartilage in the knee torn ligament: tear in one of the four ligaments in the knee — the most commonly injured ligament is the anterior cruciate ligament (ACL) bone tumors: osteosarcoma (second most prevalent bone cancer), most commonly occurs in the knee Factors that may make chronic knee pain worse: injuries to the structure of the knee can cause bleeding and swelling and can create a chronic problem over time if not treated properly sprains and strains overuse infection bad posture and form when doing physical activity not warming up or cooling down before or after physical activity improperly stretching the muscles