Which results of spine exam suggest ankylosing spondylitis (AS)?

Updated: Feb 02, 2021
  • Author: Lawrence H Brent, MD; Chief Editor: Herbert S Diamond, MD  more...
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Stiffness of the spine and kyphosis resulting in a stooped posture are characteristic of advanced-stage AS. Earlier in the course of the disease, indirect evidence of sacroiliitis and spondylitis may be observed, including tenderness of the SI (elicited by either direct pressure or indirect compression) or a limited spinal ROM. Some patients may have a deformity of the spine, most commonly with a loss of lumbar lordosis and accentuated thoracic kyphosis.

The ROM of the lumbar spine can be assessed using various methods, of which the Schober test is the most popular. (This test is not specific for AS.)

Perform the Schober test by marking a 10-cm length of the lumbar spine (with the patient in the erect position), starting at the fifth lumbar spinous process. Instruct the patient to flex his or her spine maximally. Remeasure the distance between the marks. Normal flexion increases the distance by at least 5 cm.

Loss of chest expansion (< 3-cm difference between minimum and maximum chest diameter) is usually found only in patients with late-stage disease. It is generally not helpful in diagnosis.

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