Axial spondyloarthritis (including ankylosing spondylitis)
Exam Tips
- In OSCEs, distinguish inflammatory from mechanical back pain: improves with movement, not rest; prolonged morning stiffness; night pain.
- Normal CRP/ESR does not exclude axSpA; integrate history, exam, and imaging.
- X-ray can be normal early; MRI sacroiliac joints detects active inflammation earlier (See Figure: STIR sacroiliitis pattern).
- Always screen for extra-articular disease (uveitis, psoriasis, IBD) because it changes drug choice and urgency.
- Red flag in viva: rigid osteoporotic spine has high fracture risk even after minor trauma; maintain low threshold for urgent spinal imaging.
Definition
Axial spondyloarthritis (axSpA) is a chronic immune-mediated inflammatory disease that primarily affects the sacroiliac joints and spine, causing inflammatory back pain and progressive stiffness. It includes non-radiographic axSpA (no definite X-ray change) and radiographic axSpA/ankylosing spondylitis (structural sacroiliitis on X-ray), which are now viewed as a disease spectrum with overlapping clinical burden and treatment response.
Pathophysiology
axSpA arises in genetically predisposed people (especially HLA-B27 and other MHC-associated variants) through interaction with environmental and host factors. Inflammation is centred at entheses and adjacent bone (enthesitis/osteitis), with cytokine pathways including TNF-alpha and IL-17 driving pain, stiffness, and erosive damage. Over time, repair is dysregulated, producing syndesmophytes and new bone formation that can bridge vertebrae and reduce spinal mobility. Gut-joint immune crosstalk is important: altered microbiome, increased gut permeability, and subclinical gut inflammation may amplify systemic inflammation and worsen prognosis.
Risk Factors
- HLA-B27 positivity (strongest single genetic association; absolute risk still low in many carriers)
- Family history of spondyloarthritis, uveitis, psoriasis, or inflammatory bowel disease
- Male sex for radiographic disease (non-radiographic disease affects men and women similarly)
- Current smoking (associated with onset/progression and worse structural outcomes)
- Personal history of psoriasis, inflammatory bowel disease, or previous juvenile idiopathic arthritis
- Younger age at symptom onset (typically <45 years)
Clinical Features
Symptoms
- Chronic back pain >3 months with inflammatory pattern (insidious onset, morning stiffness, nocturnal second-half pain, improves with exercise not rest)
- Alternating buttock pain (sacroiliac involvement)
- Peripheral joint pain/swelling (for example hips, shoulders, or asymmetric lower-limb arthritis)
- Enthesitis (classically heel pain at Achilles insertion or plantar fascia)
- Fatigue and reduced physical function
- Acute anterior uveitis symptoms: painful red eye, photophobia, blurred vision
- GI symptoms suggestive of inflammatory bowel disease and/or psoriasis skin/nail symptoms
Signs
- Reduced spinal flexion and extension (for example reduced modified Schober measurement)
- Reduced chest expansion
- Sacroiliac tenderness and reduced spinal mobility
- Loss of lumbar lordosis or increasing thoracic kyphosis in advanced disease
- Peripheral enthesitis tenderness (Achilles/plantar fascia)
- Features of extra-musculoskeletal disease (uveitis, psoriasis, IBD stigmata)
Investigations
Management
Lifestyle Modifications
- Structured exercise and physiotherapy (posture, spinal mobility, chest expansion, strength)
- Smoking cessation (linked to slower progression and better response to therapy)
- Education on chronic disease course, flare self-management, and adherence
- Occupational and mental health support for fatigue, pain, anxiety/depression impact
- Vaccination review before immunosuppressive therapy (avoid live vaccines once significantly immunosuppressed)
Pharmacological Treatment
NSAIDs (first-line symptomatic treatment)
- Naproxen 500 mg twice daily orally
- Ibuprofen 400-600 mg three times daily orally (max 2.4 g/day in divided doses)
- Diclofenac 50 mg three times daily orally (or 75 mg modified-release twice daily)
Use lowest effective dose for shortest period; trial up to 2 different NSAIDs at adequate dose before escalation. Co-prescribe gastroprotection when indicated (for example omeprazole 20 mg once daily). Cautions/contraindications: active peptic ulcer, significant renal impairment, uncontrolled hypertension, heart failure, high cardiovascular risk, anticoagulation-related bleeding risk; NSAIDs can worsen inflammatory bowel disease in some patients.
Simple analgesia adjunct
- Paracetamol 1 g up to four times daily (max 4 g/day)
Adjunct only; does not treat inflammation. Check total daily paracetamol from combination products and liver risk.
Biologic DMARDs for persistent active disease under specialist care
- Adalimumab 40 mg subcutaneously every other week
- Etanercept 50 mg subcutaneously once weekly
- Certolizumab pegol 400 mg at weeks 0, 2, 4 then 200 mg every 2 weeks (or 400 mg every 4 weeks)
- Golimumab 50 mg subcutaneously monthly
- Secukinumab 150 mg subcutaneously weekly for 5 doses then monthly
Selection guided by NICE technology appraisals, comorbidity (uveitis/IBD/psoriasis), and prior biologic response. Mandatory pre-treatment infection screening (TB, hepatitis B/C, HIV as appropriate). Do not start during active serious infection; caution in demyelinating disease and moderate-severe heart failure with TNF inhibitors; monitor for sepsis, cytopenias, hepatotoxicity, and injection reactions.
Targeted synthetic DMARD (specialist use in selected patients)
- Upadacitinib 15 mg once daily orally
Used in selected refractory cases per UK guidance. Safety: risk of serious infection, herpes zoster, venous thromboembolism, major adverse cardiovascular events, and malignancy signals in high-risk groups; avoid in pregnancy and use strong contraception advice where relevant.
Local corticosteroid injection (for focal peripheral inflammation)
- Intra-articular triamcinolone (dose varies by joint size)
May help peripheral joint/enthesis flares; long-term systemic oral steroids are generally not routine therapy for axial disease.
Surgical / Interventional
- Total hip replacement for severe destructive hip disease
- Corrective spinal osteotomy in carefully selected severe fixed deformity
- Urgent spinal surgical assessment for unstable vertebral fracture or neurological compromise
Complications
- Progressive spinal stiffness, kyphotic deformity, and reduced mobility from syndesmophyte formation
- Osteoporosis and increased vertebral fracture risk (fracture may occur after minimal trauma)
- Spinal cord injury risk after cervical or thoracolumbar fractures in rigid spine
- Extra-musculoskeletal disease: recurrent anterior uveitis, psoriasis, inflammatory bowel disease
- Cardiovascular morbidity including valvular disease and heart failure risk
- Restrictive ventilatory defect from costovertebral/chest wall involvement
- Psychological morbidity (anxiety/depression), reduced quality of life, work disability
Prognosis
Course is heterogeneous: many patients have relapsing-remitting activity, while persistent inflammation can cause slow but irreversible structural damage over years. A minority with non-radiographic axSpA progress to radiographic disease (roughly 5-10% over 2 years and up to 30% over 10 years in some cohorts). Better outcomes are associated with earlier diagnosis, shorter disease duration, lower baseline disability, and good response to first biologic therapy.
Sources & References
💊BNF Drug References(5)
- Bimekizumab[management.pharmacological]
- Certolizumab pegol[management.pharmacological]
- Ixekizumab[management.pharmacological]
- Secukinumab[management.pharmacological]
- Upadacitinib[management.pharmacological]