Psoriatic arthritis is a chronic inflammation of the joints in people with psoriasis or genetic predisposition to psoriasis. Psoriasis is a chronic, autoimmune disease that appears on the skin as red scaly patches. About one in ten people with psoriasis also develop psoriatic arthritis. The onset of psoriatic arthritis most commonly occurs in the fourth or fifth decades of life. The arthritis frequently involves the knees, ankles, and joints of the feet. It presents with joint stiffness which is typically worse in the morning, or joint pain. It is important to get correctly diagnosed as well as treated, as untreated psoriatic arthritis can cause joint changes. The treatment of psoriatic arthritis usually involves oral anti-inflammatory medications, more aggressive oral disease-modifying medications, or injectable biologic agents such as Enbrel, Humira and Stelara.