What is reactive arthritis? Reactive arthritis is pain or swelling in a joint that is caused by an infection in your body. You may also have red, swollen eyes and a swollen urinary tract. These symptoms may occur alone, together, or not at all. Most people with reactive arthritis recover fully from the first flare of symptoms and can return to regular activities 2 to 6 months later. Some people will have long-term, mild arthritis. A few patients will have long-term, severe arthritis that is difficult to control with treatment and may cause joint damage.