Psoriatic arthritis occurs in less than 10% of people with psoriasis. Its treatment often requires consultation with a rheumatologist in addition to treatment of the skin lesions by a dermatologist. It occurs most frequently in psoriasis patients whose disease is active, especially in persons with the pustular type of psoriasis. Occasionally it appears in a person who has no signs or symptoms of psoriasis, in which case it must be diagnosed by its unique laboratory test results. Psoriasis of the fingernails and toenails is associated with a higher incidence of psoriatic arthritis. Symptoms of psoriatic arthritis resemble those of rheumatoid arthritis, although the diseases are otherwise quite different. Arthritis changes cause deterioration and pain in small joints of the hands and feet, large joints of the legs and spine, and tendons. Nonspecific foot pain or “tennis elbow” may be an early symptom to appear and may be overlooked if not associated with psoriatic skin or nail lesions.