Arthritis could be divided into the following types according to their etiology.
1. Osteoarthritis (OA), is the most common form of joint disease involves progressive loss of articular cartilage and reactive changes at joint margins and in subchondral bone. It is a degenerative joint disease that seems almost inescapable in old age.
2. Rheumatoid Arthritis (RA), is a chronic systemic inflammatory disease of unknown etiology with a predilection for joint involvement. Articular inflammation may be remitting, but if continued usually results in joint damage and disability.
3. Others, such as Infectious Arthritis, Psoriatic Arthritis, etc.
By location, arthritis could affect joints most commonly seen at hip joints, knee joints, elbow joints, spine joints, shoulder joints, toe/finger joints and hand/wrist joints.