How are joints affected by peripheral enthesitis in ankylosing spondylitis (AS) and undifferentiated spondyloarthropathy (USpA)?

Updated: Feb 02, 2021
  • Author: Lawrence H Brent, MD; Chief Editor: Herbert S Diamond, MD  more...
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Enthesopathic lesions tend to be quite painful (eg, the plantar fascia when getting out of bed), especially in the morning. Some of the peripheral arthritis occurs at sites in which the major component is local enthesitis, as suggested by magnetic resonance imaging (MRI).

Joint involvement tends to occur most commonly in the hips, shoulders, and joints of the chest wall, including the acromioclavicular and sternoclavicular joints, and often occurs in the first 10 years of disease. Involvement of the hips and shoulders may result in joint damage with radiographic changes. Involvement of the hips and shoulder joints is more common in persons with juvenile-onset AS than in adults with AS.  In addition, involvement of the tarsal joints occurs more comonly in juvenile-onset AS; it is sometimes called ankylosing tarsitis.

Other peripheral joints are involved less frequently and to a milder degree, usually as an asymmetric oligoarthritis predominantly involving the lower extremities. Involvement of the temporomandibular joint (TMJ) occurs in approximately 10% of patients. Patients may complain of decreased range of motion (ROM) or jaw pain. Involvement of the costovertebral and costotransverse joints can lead to decreased ROM and restriction in respiration. Patients may complain of difficulty breathing or chest tightness.

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