Approach to Low Back Pain & Stiffness
Ankylosing Spondylitis • Axial Spondyloarthritis • MRCP (UK) PACES
A structured PACES approach to a patient presenting with inflammatory low back pain and stiffness. Learn how to recognise Ankylosing Spondylitis, identify extra-articular manifestations, perform a focused examination and explain investigations and modern treatment.
At a Glance
Red Flags
PACES Approach
Extra-articular Manifestations
Anterior uveitis
Aortic regurgitation
Conduction block
Apical fibrosis
Restrictive lung disease
Amyloidosis
IgA nephropathy
Achilles tendinitis
Inflammatory bowel disease
Overview
Ankylosing spondylitis is a chronic inflammatory disease affecting the axial skeleton and sacroiliac joints. Patients typically present with inflammatory low back pain, prolonged morning stiffness and progressive restriction of spinal movement that improves with exercise. In MRCP (UK) PACES, candidates should recognise the characteristic pattern of inflammatory back pain, identify extra-articular manifestations such as anterior uveitis, aortic regurgitation and apical pulmonary fibrosis, perform a focused musculoskeletal examination and explain long-term multidisciplinary management. :contentReference[oaicite:0]{index=0}
Structured History
- Onset and duration of low back pain
- Morning stiffness lasting more than 30 minutes
- Pain improving with exercise but not with rest
- Night pain causing waking during the second half of the night
- Alternating buttock pain or hip pain
- Peripheral joint pain or swelling
- Heel pain suggesting Achilles tendinitis or plantar fasciitis
- Episodes of painful red eye with blurred vision (anterior uveitis)
- Symptoms of inflammatory bowel disease or psoriasis
- Breathlessness, palpitations, chest pain or frothy urine suggesting extra-articular disease
Examination
- Observe posture for thoracic kyphosis and loss of lumbar lordosis
- Assess gait and overall spinal mobility
- Measure cervical spine movements
- Assess lumbar flexion using the Modified Schober Test
- Measure occiput-to-wall distance
- Assess chest expansion
- Examine sacroiliac joints and hips
- Inspect heels for Achilles enthesitis
- Cardiovascular examination for aortic regurgitation
- Respiratory examination for apical fibrosis and restrictive lung disease
Differential Diagnosis
Investigations
- Inflammatory markers (ESR and CRP)
- Full blood count
- HLA-B27 testing
- X-ray of the sacroiliac joints and lumbar spine
- MRI sacroiliac joints for early disease
- Renal function and urine analysis
- Chest X-ray or HRCT if pulmonary involvement suspected
- Pulmonary function tests
- Echocardiography for suspected aortic regurgitation
- Ophthalmology assessment if anterior uveitis is suspected
Diagnosis
Ankylosing Spondylitis (Axial Spondyloarthritis)
The diagnosis is suggested by inflammatory low back pain, prolonged morning stiffness, reduced spinal mobility and restricted chest expansion. The presence of anterior uveitis, enthesitis, inflammatory bowel disease or psoriasis further supports the diagnosis.
Management
Explaining to the Patient
"Your symptoms are most consistent with Ankylosing Spondylitis, an inflammatory condition affecting the spine and sacroiliac joints. It can also affect the eyes, heart, lungs and other joints. Although there is no cure, early treatment with exercise, medication and regular follow-up can control symptoms, reduce inflammation and help maintain mobility."
Examiner's Corner
What are your clinical findings?
- Reduced spinal mobility
- Loss of lumbar lordosis with exaggerated thoracic kyphosis
- Reduced chest expansion
- Restricted cervical spine movements
- Positive Modified Schober Test
- Increased occiput-to-wall distance
- Features of enthesitis (especially Achilles tendon)
Extra-articular manifestations
Common Viva Questions
- What is inflammatory back pain?
- What is the role of HLA-B27?
- Which imaging modality detects early disease?
- How do you assess spinal mobility?
- What are the extra-articular manifestations?
- When should biologic therapy be started?
- Which complications require urgent referral?
Investigations & Treatment
- ESR and CRP
- HLA-B27 testing
- X-ray and MRI of sacroiliac joints
- Exercise and physiotherapy for all patients
- NSAIDs as first-line drug therapy
- TNF or IL-17 inhibitors for active disease
Pathfinder Pearls
Common Pitfalls
- Confusing inflammatory back pain with mechanical back pain.
- Failing to assess spinal mobility objectively.
- Not measuring chest expansion.
- Missing anterior uveitis in a patient with a painful red eye.
- Ignoring cardiac or pulmonary complications.
- Relying solely on HLA-B27 to make the diagnosis.
- Not emphasising the importance of lifelong exercise and physiotherapy.
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