What is arthritis? Arthritis is a general term for more than 100 diseases that cause inflammation, pain, stiffness and swelling of joints. Common types of arthritis include: Osteoarthritis - an ongoing, progressive disease that affects the joints as cartilage breaks down over time. Osteoarthritis is also called degenerative joint disease. Rheumatoid arthritis - an autoimmune disease that affects the joints of the body with episodes of painful inflammation. Rheumatoid arthritis also affects other organs of the body and can result in the destruction of joints, disability, and, in severe cases, life-threatening complications. Septic arthritis - arthritis caused by the infection of a joint by microorganisms, such as bacteria or fungi. Complications of all forms of arthritis can be serious and include destruction of the joints, leading to disability. Rheumatoid arthritis and septic arthritis can also lead to serious or life-threatening complications that can affect almost any organ in the body. Seek prompt medical care if you have symptoms of arthritis, such as inflammation, pain, stiffness, and swelling of joints. Early diagnosis and treatment can minimize discomfort and reduce the risk of serious complications.