Psoriatic arthritis is a distinct disease, different from rheumatoid arthritis and ankylosing spondylitis- another common type of arthritis- but sharing similar features to each. The disability and functional impairment in psoriatic arthritis can be as severe as that occurring from rheumatoid arthritis.

Typically, a patient will have had psoriasis for a number of years before the arthritis develops. A small proportion of patient will develop the arthritis concurrently with the skin disease and an even smaller percentage will develop the skin disease after the joint disease.

Psoriatic arthritis may affect most joints in an oligoarticular pattern, meaning a few scattered joints are affected and the joint inflammationdoes not have the symmetrical pattern seen in rheumatoid arthritis. Enthesitis, which is inflammation of the tendons that attach to bone, is common in psoriatic arthritis.