Several years after psoriasis has broken out, the patient may be affected by psoriatic arthritis. This is an inflammatory, chronic arthritis with variable degrees of joint manifestations. It involves peripheral joints (hips, shoulders, hands, and feet) in 70% of cases. About 10 percent to 30 percent of people with psoriasis also develop psoriatic arthritis, which causes pain, stiffness, and swelling in and around the joints. It appears between the ages of 30 and 50 and seems to affect men slightly more than women.