Ankylosing Spondylitis

Disclaimer: Please read the Disclaimer at the bottom of this page.
Copyright © Educom Pty Ltd: All material on this website (including the text, graphics, videos and downloadable files) is owned by or licensed to Educom Pty Ltd and is subject to copyright and other intellectual property rights under international conventions

Ankylosing Spondylitis

Ankylosing Spondylitis is a polyarthropathy involving chronic inflammation of the axial skeleton (Axial Spondyloarthritis), including the spinal, sacroiliac, costovertebral, manubriosternal, sternoclavicular, and costochondral joints. Ankylosing Spondylitis may also affect the joints of the appendicular skeleton (e.g., hip and shoulder), as well as the entheses (the site of attachment of tendon, ligament, fascia, or capsule to bone).

There is a strong genetic predisposition with 97% of those affected having a family history of Ankylosing Spondylitis. Approximately 6.5% of individuals with HLA-B27 develop Ankylosing Spondylitis. 90% of patients who have Ankylosing Spondylitis are HLA-B27 positive.

The initial presentation typically involves the sacroiliac joints, followed by the involvement of the intervertebral discs, apophyseal joints, costovertebral joints, costotransverse joints, and paravertebral ligaments. Early pathology produces subchondral granulation tissue that erodes the joint and is subsequently replaced by fibrocartilage which ultimately leads to ossification.

Features of Inflammatory Back Pain

Patients with Ankylosing Spondylitis typically present with clinical features of inflammatory back pain. According to the SpondyloArthritis International Society (ASAS), patients with chronic back pain (>3 months) are considered to have inflammatory back pain if they exhibit at least four of the following five features:

• Pain at night (with improvement upon rising)
• Insidious onset
• Improvement with exercise
• No improvement with rest
• Age of onset <40 years

Other Features of Ankylosing Spondylitis

• Back stiffness that is worse when rising in the morning, and which eases with activity
• A dull pain in the lower back and buttocks lasting >3 months
• Buttock pain that often alternates from side to side
• Pain and stiffness that progress over time to include the thoracic and cervical regions
• A marked improvement in pain with the use of NSAIDs (within 24 to 48 hours)
• Peripheral arthropathy and enthesitis (present in approximately 33% of cases)
• Pain and stiffness in other joints including those of the shoulder girdle, anterior chest (manubriosternal, sternoclavicular, and costochondral inflammation), symphysis pubis, and TMJ
• Pain may also be reported in the hip, ischial tuberosity, and heel
• Uveitis may be seen in some patients
• A family history of Ankylosing Spondylitis
• More commonly found in males

• Postural examination in established Ankylosing Spondylitis may reveal hypolordosis in the lumbar region and hyperkyphosis in the thoracic region
• A global loss of range of motion in the lumbopelvic region
• A loss of lumbar flexion (e.g., demonstrated by the Modified Schober test)
• Positive sacroiliac joint provocation tests
• Flexion deformity of the cervical spine
• A loss of thoracic and cervical ranges of motion (e.g., demonstrated by the Tragus to Wall test)
• Tenderness on palpation over the sacroiliac joints
• Reduced chest expansion (e.g., demonstrated by the Thoracic Expansion test)
• Flexion deformity of the hips
• Approximately 25 to 35% have anterior uveitis
• Palpation may reveal tenderness over the calcaneus (Achilles tendon and plantar fascia insertions)
• Dactylitis (swelling of the fingers or toes) may be present

Sacroiliac Joints

• Early manifestation: Symmetrical and bilateral sacroiliitis
• Disease progression: Subchondral erosions, sclerosis, and bony proliferation on the iliac side of the sacroiliac joints
• Late-stage: Complete ankylosis

Spine

• Early Signs: A squaring of the vertebral bodies
• Disease progression: Diffuse syndesmophytosis leading to ankylosis (Bamboo Spine)

• HLA-B27 positive
• Elevated ESR
• Elevated C-Reactive Protein

Differential Diagnosis

• Reactive Arthritis (a brief summary is presented below)
• Mechanical Back Pain
• Osteoarthritis
• Psoriatic Arthritis
• Diffuse Idiopathic Skeletal Hyperostosis (also known as DISH or Forestier’s Disease)
• Arthritis associated with Inflammatory Bowel Disease

Reactive Arthritis

Reactive Arthritis (formerly referred to as Reiter’s Syndrome) is a spondyloarthritis that is associated with a preceding or concomitant infection, most typically involving the gastrointestinal or genitourinary systems. The clinical presentation usually begins one to four weeks following the antecedent infection. The classic triad of large joint inflammation (e.g., knee), conjunctivitis, and urethritis have been reported to be present in only about one-third of cases. The natural history of Reactive Arthritis is that of complete resolution of symptoms within 6 to 12 months. Plain radiography is of limited value as there are no syndrome-specific radiological findings.

When clinical evaluation reveals features of inflammatory back pain, the patient should be referred to a medical practitioner for further investigation. When Ankylosing Spondylitis is suspected, imaging and laboratory testing are required.