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.
What is fibromyalgia? Fibromyalgia is a long-lasting disorder that causes pain and tenderness throughout the body. It also can cause you to feel overly tired (fatigue) and have trouble sleeping. Doctors do not fully understand what causes fibromyalgia, but people with the disorder are more sensitive to pain.