Reactive arthritis is a general term for a form of joint inflammation (arthritis) that develops as a "reaction" to an infection in another area of the body (i.e., outside of the joints). Joint inflammation is characterized by redness, swelling, pain and warmth in and around the affected joint. In reactive arthritis, the joints of the lower limbs are most often affected. Two other common symptoms of reactive arthritis are inflammation of the urinary tract and inflammation of the membrane (conjunctiva) that lines the eyelids (conjunctivitis). These three characteristic symptoms may occur separately, all at once or not at all. Additional symptoms such as fever, weight loss, lower back pain and heel pain may also occur. Reactive arthritis usually develops following a bout with certain bacterial infections including Chlamydia, Salmonella, Shigella, Yersinia, and Campylobacter.
Reactive arthritis belongs to a group of related disorders known as the spondyloarthropathies. These disorders are linked by the association of similar symptoms and a specific genetic marker called HLA-B27. Symptoms common to these disorders include arthritis, especially of the lower limbs, lower back pain and enthesitis, a condition characterized by inflammation at the spot where skeletal muscle attaches to bone. This group of disorders includes reactive arthritis, ankylosing spondylitis, psoriatic arthritis, undifferentiated spondyloarthritis and spondyloarthritis associated with inflammatory bowel disease.
Reactive arthritis is a poorly defined disorder that has been described in the medical literature under many different names. No precise diagnostic or classification criteria have been developed that are universally agreed upon in the medical community.