Psoriasis is a skin disease that causes patches of itchy, red skin with a silver, scaly appearance. The lesions can occur on any part of the body, but common areas include elbows, knees, back, face, scalp, palms, and feet.
With psoriatic arthritis, people with psoriasis also have arthritis that causes pain, stiffness, and inflammation of the joints. Although the arthritis is typically mild with occasional flare-ups, in some people, it is continuous and can cause joint damage if not treated.