What is reactive arthritis? Reactive arthritis happens when an infection causes joint pain and swelling. A bacterial infection in the digestive or urinary tract or the genitals usually triggers the condition, but arthritis symptoms typically do not start until a few weeks after you have recovered from the infection. The most common features of reactive arthritis are inflammation of the joints (especially the knees and ankles), eyes, and urinary tract, but not everyone gets all three, or they might not happen at the same time.
Two types of antibody molecules act in concert to stimulate inflammation in people with rheumatoid arthritis, according to research funded in part by the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS).