Arthritis comes in many forms.
Osteoarthritis can affect one large joint, such as the hip or knee, or it may affect several joints. It can also affect the fingers or feet. See What are the common symptoms of osteoarthritis?
Secondary osteoarthritis is not a separate type of arthritis, but it is osteoarthritis caused by another condition. See What causes osteoarthritis?
Erosive inflammatory osteoarthritis is a rare type of osteoarthritis that causes a severe inflammation of the middle or end joints of the fingers. This eventually leads to deformity and fusion of these joints.