Which joints, axial skeleton, and entheses findings are characteristic of reactive arthritis (ReA)?

Updated: Dec 24, 2020
  • Author: Carlos J Lozada, MD; Chief Editor: Herbert S Diamond, MD  more...
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Articular involvement in ReA is typically asymmetric and usually affects the weight-bearing joints (ie, knees, ankles, and hips), but the shoulders, wrists, and elbows may also be affected. In more chronic and severe cases, the small joints of the hands and feet may be involved as well. Dactylitis (ie, sausage digits) may develop. In children, joint involvement is oligoarticular in 69% of cases, polyarticular in 27%, and monoarticular in 4%.

Joints are commonly described as tender, warm, swollen (see the image below), and, sometimes, red. Symptoms may occur initially or several weeks after onset of other symptoms. Migratory or symmetric involvement is also reported. Periostitis and tendinitis may occur, especially involving the Achilles tendon, which produces pain in the heel. The arthritis is usually remittent and rarely leads to severe limitation of functional capacity. Muscular atrophy can develop in severely symptomatic cases.

Swelling of right knee with effusion caused by art Swelling of right knee with effusion caused by arthritis. Image courtesy of Gun Phongsamart, MD.

Enthesopathy, or enthesitis (ie, inflammation of ligament and tendon insertions into bone), is thought to be a characteristic feature of ReA. The Achilles insertion is the most common site; other sites include the plantar fascial insertion on the calcaneus, ischial tuberosities, iliac crests, tibial tuberosities, and ribs.

Sacroiliitis (see the image below) frequently occurs in adults who are positive for human leukocyte antigen (HLA)–B27 (though it is apparently less common in children). It is typically self-limiting. Whereas 50% of patients with ReA may develop low-back pain, most physical examination findings in patients with acute disease are minimal except for decreased lumbar flexion. Patients with more chronic and severe axial disease may develop physical findings similar to, or even indistinguishable from, those of ankylosing spondylitis.

Remarkable tenderness of left sacroiliac joint cau Remarkable tenderness of left sacroiliac joint caused by sacroiliitis. Image courtesy of Gun Phongsamart, MD.

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