ReA typically occurs anywhere from 3 days to 6 weeks after the antecedent infection. It may involve one or more joints, though usually six or fewer. ReA commonly afflicts the lower extremities, especially the knees and/or ankles, and is often asymmetric. Less frequently, the upper extremities may be affected, including the wrists, elbows, and fingers. Joints can be hot, painful, and swollen, with accumulation of fluid (effusion) in the articular space. Back pain may be present, secondary to involvement of the spine or sacroiliac joints (sacroiliitis). There may also be enthesitis, or inflammation of the entheses, where tendon attaches to bone, resulting in pain at the kneecap, heel, or other locations. The Achilles tendon and plantar fascia attachment to the calcaneus are common sites. Another finding can be dactylitis, a term describing “sausage-like” digits. Aside from joint involvement, ReA can include conjunctivitis, genitourinary inflammation, and skin and nail changes.
