Reactive arthritis is joint pain and swelling triggered by an infection in another part of your body, usually your intestines, genitals or urinary tract. The joints in your knees, ankles and feet are the usual targets of reactive arthritis. Reactive arthritis is sometimes called Reiter's syndrome, Reiter's is actually a specific type of reactive arthritis. Reactive arthritis isn't common. For most people, signs and symptoms of reactive arthritis come and go, eventually disappearing within 12 months.