NIAMS Health Information on Reactive Arthritis

Overview ofReactive ArthritisReactive arthritis, as the name suggests, occurs in reaction to something—in this case, an infection. The condition is caused by a bacterial infection in the digestive or urinary tract or the genitals, but arthritis symptoms typically do not set in until after you have recovered from the infection. Inflammation of the joints, eyes, and urinary tract are hallmarks of reactive arthritis, but not everyone gets all three, or they might not occur at the same time.The knee and ankle joints are frequently affected, and many people also experience pain in the sacroiliac joints, which are located in the lower back. Reactive arthritis is a form of spondyloarthritis, a group of arthritis conditions that typically involve the sacroiliac joints in the lower back, and entheses (places where tendons or ligaments attach to bones). Foot pain in people with reactive arthritis is usually due to inflammation of entheses.The symptoms often clear up on their own within a few wee...