PassFinals
Musculoskeletal

Ankylosing spondylitis

Radiographic axial spondyloarthritis causing inflammatory back pain, sacroiliitis and progressive structural new bone formation in susceptible people.

In a nutshell

Ankylosing spondylitis is radiographic axial spondyloarthritis: inflammatory back pain, sacroiliitis and progressive structural change. Normal HLA-B27, inflammatory markers or X-ray does not exclude axial disease.

Classic presentation

Insidious back or buttock pain beginning before 45, worse at night or rest and improved by movement, with morning stiffness and later reduced spinal mobility.

Key points

  • Inflammatory back pain improves with movement and worsens with rest.
  • Radiographic ankylosing spondylitis is part of the wider axial spondyloarthritis spectrum.
  • Normal CRP, ESR, HLA-B27 or initial X-ray does not exclude the diagnosis.
  • Use sacroiliac X-ray first when appropriate, then inflammatory-protocol MRI if non-diagnostic.
  • Start structured exercise and NSAID symptom control; assess active disease for advanced therapy in specialist care.
  • A painful red eye with photophobia or blurred vision needs same-day ophthalmology.
  • New severe spinal pain after trauma in a rigid spine is a fracture emergency.

First-line investigation

Inflammatory back-pain assessment, sacroiliac X-ray followed by inflammatory-protocol MRI when needed, with CRP/ESR and HLA-B27 as supportive tests.

Management

Recognise and refer

  • Refer the inflammatory back-pain pattern to rheumatology and act urgently on uveitis, neurological symptoms or suspected spinal fracture.1,2

Control pain and preserve mobility

  • Use structured exercise and physiotherapy with an NSAID at the lowest effective dose, switching NSAID if needed after an adequate trial and monitoring risk.1,5

Treat active disease with advanced therapy

  • When active disease remains uncontrolled, use NICE eligibility criteria and the current BSR axial guideline to select a biologic or targeted synthetic DMARD under specialist care.1,3,5

Coordinate extra-articular care

  • Discuss uveitis, psoriasis and inflammatory bowel disease before selecting advanced therapy and coordinate rheumatology with the relevant specialties.1,4,3

Prevent fracture and disability

  • Monitor function, activity, mobility, bone health and treatment safety; assess new severe spinal pain after trauma urgently.1,3

Exam traps

  • A negative HLA-B27 does not rule out axial spondyloarthritis.
  • Normal inflammatory markers do not rule it out.
  • A normal X-ray does not exclude early or non-radiographic disease.
  • Same-day ophthalmology is required for acute anterior uveitis symptoms.
  • A fused spine can fracture after apparently minor trauma.

Illustrations

Bamboo spineLateral thoracic spine radiograph showing marginal syndesmophytes bridging multiple vertebral bodies to create the bamboo-spine appearance of advanced ankylosing spondylitis.James Heilman, MD, Wikimedia Commons · CC-BY-SA-4.0
Enthesitis versus synovitisDiagram contrasting inflammation at tendon and ligament entheses in spondyloarthritis with synovial inflammation in rheumatoid arthritis.PassFinals · original
Active sacroiliitis on MRICoronal MR images showing focal active inflammation at the sacroiliac joint as an imaging feature of axial spondyloarthritis.Fiona McQueen, Marissa Lassere and Mikkel Østergaard, Wikimedia Commons · CC-BY-2.0

Key sources

  1. NICE NG65: Spondyloarthritis in over 16s: diagnosis and management (UK referral, imaging, exercise, NSAID, advanced therapy and complication guidance; reviewed March 2025.)Updated 4 Mar 2025
  2. NHS: Ankylosing spondylitis (UK information on axial symptoms, exercise, treatment and complications.)
  3. British Society for Rheumatology: 2025 guideline for axial spondyloarthritis with biologic and targeted synthetic DMARDs (Current UK specialist guidance for advanced therapy selection and monitoring in axial spondyloarthritis.)Updated 9 Apr 2025
  4. NICE CG153: Psoriasis: assessment and management (UK psoriatic arthritis screening, referral and coordinated psoriasis care.)
  5. BNF online (Check current NSAID, biologic and targeted therapy prescribing, contraindications, interactions and monitoring.)

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.