The disease that may be most similar to osteoarthritis is rheumatoid arthritis. While their symptoms are similar, the causes of osteoarthritis and rheumatoid arthritis are strikingly different. The former occurs primarily due to wear and tear on the joint. Lupus, an autoimmune disease like RA, that causes inflammation in the joints, as well as in the tendons, skin and other connective tissues. 2  Gout, which occurs when uric acid crystals build up in the joints, and causes joint inflammation, pain and tenderness.