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Ankylosing Spondylitis

Ankylosing spondylitis (AS), is a chronic condition of the spine that causes dull lower back pain and early morning stiffness in the back.

1- The symptoms are unilateral to begin with but become bilateral as the disease progresses. It causes significant disability affecting the quality of life.2

Stages of AS:3
The disease is staged according to radiographic findings.3 Based on the radiologic findings, the patient may belong to Stages I – IV or Stage V indicating severe joint involvement , possible disability and requiring surgery.2,3 The joints primarily affected are the spine and the bones joining the spine to the pelvis. Sometimes, the shoulders, ankles or knees may also be involved.

Table 1: Criteria for diagnosis

  1. Clinical criteria:
  • Low back pain and stiffness for more than three months, which improves with exercise, but is not relieved by rest
  • Limitation of motion of the lumbar spine in both the sagittal and frontal planes.
  • Limitation of chest expansion relative to normal values correlated for age and sex
  1. Radiological criterion:

    Sacroiliitis grade >2 bilaterally or grade 3-4 unilaterally

-Definite AS if the radiological criterion is associated with at least on clinical criterion.

Source: van der Linden S, Valkenburg HA, Cast A. Arthritis Rheum. 1984;27:361-368.


Apart from the clinical criteria in Table 1, an elevated C-reactive protein is found in about 50% of the patients. Inflammatory markers and anemia are observed. Young males with a human leukocyte antigen B27 (HLA-B27) are at risk but it is possible to have the disease without having the gene and hence the test is not very specific.2


  1. Taurog JD, Chhabra A, Colbert RA. Ankylosing spondylitis and axial spondyloarthritis. New England Journal of Medicine. 2016 Jun 30;374(26):2563-74.
  2. Ryall NH, Helliwell P. A critical review of ankylosing spondylitis. Critical Reviews™ in Physical and Rehabilitation Medicine. 1998;10(3).
  3. van der Linden S, Valkenburg HA, Cats A. Evaluation of diagnostic criteria for ankylosing spondylitis. A proposal for modification of the New York criteria. Arthritis Rheum 1984; 27:361–368.