• Clinical science

Ankylosing spondylitis (Bekhterev's disease…)


Ankylosing spondylitis (spondyloarthritis) is a chronic inflammatory disease of the axial skeleton that leads to partial or even complete fusion and rigidity of the spine. Males are disproportionately affected and upwards of 90% of patients are positive for the HLA-B27 genotype, which predisposes to the disease. The most characteristic early finding is pain and stiffness in the neck and lower back, caused by inflammation of the vertebral column and the sacroiliac joints. The pain typically improves with activity and is especially prominent at night. Other articular findings include tenderness to percussion and displacement of the sacroiliac joints (Mennell's sign), as well as limited spine mobility, which can progress to restrictive pulmonary disease. The most common extra-articular manifestation is acute, unilateral anterior uveitis. Diagnosis is primarily based on symptoms and x-ray of the sacroiliac joints, with HLA-B27 testing and MRI reserved for inconclusive cases. There is no curative treatment, but regular physiotherapy can slow progression of the disease. Additionally, NSAIDs and/or tumor necrosis factor-α inhibitors may improve symptoms. In severe cases, surgery may be considered to improve quality of life.


  • Sex: > (3:1)
  • Age: 15–40 years
  • Lifetime prevalence in the US: ∼0.5%


Epidemiological data refers to the US, unless otherwise specified.


  • Genetic predisposition: 90–95% of patients are HLA-B27 positive.


Clinical features

Articular symptoms

  • Most common presenting symptoms: back and neck pain
    • Gradual onset of dull pain that progresses slowly
    • Morning stiffness that improves with activity
    • Pain is independent of positioning; , also appears at night
    • Tenderness over the sacroiliac joints
  • Limited mobility of the spine (especially reduced forward lumbar flexion)
  • Inflammatory enthesitis (e.g., of the Achilles tendon, iliac crests, tibial tuberosities): painful on palpation
  • Dactylitis
  • Arthritis outside the spine: hip, shoulder, and knee joint

Extra-articular manifestations



Diagnostic approach

  1. Physical examination, patient history, and pelvic x-ray: If results are conclusive, no additional testing is required!
  2. If inconclusive → HLA-B27 testing
  3. If still inconclusive → pelvic MRI

Clinical tests

  • Chest expansion measurement: in full expiration and inspiration
    • Pathological difference: < 2 cm
    • Physiological difference: > 5 cm
  • Spine mobility tests
  • Examination of the hip[3]

Laboratory findings



Mild courses may only exhibit inflammatory changes in the sacroiliac joints on x-ray after a number of years.


  • More sensitive than CT scan for detecting sacroiliitis [5]
  • Best method for early detection


Differential diagnoses



Radiographic features

  • Horizontal growth

Syndesmophytes grow vertically, as opposed to osteophytes, which grow horizontally!

The differential diagnoses listed here are not exhaustive.


Physical therapy is the most important treatment modality!



We list the most important complications. The selection is not exhaustive.

last updated 12/03/2019
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