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Ankylosing Spondylitis (AS) - Detailed Orthopaedic Clinical Notes

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1. DEFINITION & OVERVIEW

• Part of the seronegative spondyloarthritides group (Moll & Wright, 1970s) - includes AS, psoriatic arthritis, reactive arthritis, IBD-associated arthritis
• Also termed r-axSpA (radiographic axial spondyloarthritis) in modern classification
• Campbell's Operative Orthopaedics 15th Ed, p. 2420

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2. EPIDEMIOLOGY

• Campbell's Operative Orthopaedics, p. 2420; Harrison's 22E, p. 2926

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3. PATHOLOGY & PATHOGENESIS

Key Mechanism: Enthesitis

Progression:

1. Inflammation at enthesis → periarticular osteopenia
2. Inflammatory bone resorption → "squaring off" of vertebral bodies (Romanus lesions - sclerotic shiny corners)
3. Ossification of annulus fibrosus (Sharpey fibres) → syndesmophytes (vertical, thin, marginal)
4. Sparing of anterior longitudinal ligament initially
5. Fusion of posterior elements - facet joints, interspinous/supraspinous ligaments, ligamentum flavum
6. Final result: Bamboo spine appearance
7. Progression: caudal to cephalad (sacroiliac joints → lumbar → thoracic → cervical)

Pathological features:

• Sacroiliitis (bilateral, symmetrical) - synovial portion of SIJ first
• Costovertebral joint involvement → restricted chest expansion
• Hip involvement ("root joint") - diffuse joint space loss, entheseal new bone at femoral head
• Andersson lesion - inflammatory pseudarthrosis at mobile unfused segments (can mimic infection)
• Grainger & Allison's Diagnostic Radiology, p. 1119-1121; Campbell's p. 2420

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4. CLINICAL FEATURES

4a. Spinal Symptoms

• Inflammatory back pain (cardinal symptom): insidious onset, worse in morning/after rest, improves with activity
• Morning stiffness - lasting >30 min, improves with exercise
• Buttock pain (sacroiliac joint origin) - may alternate sides
• Progressive loss of lumbar lordosis → thoracic and cervical kyphosis
• Inability to look above the horizon ("stooped" posture)
• Inability to lie flat in bed

4b. Peripheral Manifestations

• Hip joint - most common peripheral joint (second most after SIJ overall); diffuse joint space loss
• Shoulder, knee (asymmetric, oligoarticular, lower limb predominant)
• Heel pain (calcaneal enthesopathy, Achilles enthesitis)

4c. Extra-articular (Extra-spinal) Features - "3 A's"

4d. Clinical Examination Signs

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5. DIAGNOSTIC CRITERIA

Modified New York Criteria (1984) - Gold Standard for AS

1. Low back pain for ≥3 months, improved by exercise, not relieved by rest
2. Limitation of lumbar spine motion in sagittal AND frontal planes
3. Chest expansion reduced relative to normal for age and sex

• Sacroiliitis grade ≥2 bilaterally, OR grade 3-4 unilaterally

Sacroiliitis Grading (Modified New York Criteria):

• Harrison's Principles 22E, p. 2926-2927; Firestein & Kelley's Rheumatology

ASAS Criteria (2009) - for Axial SpA (broader, includes nr-axSpA):

• Imaging arm: Sacroiliitis on MRI or X-ray + ≥1 SpA feature
• Clinical arm: HLA-B27 positive + ≥2 SpA features

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6. INVESTIGATIONS

MRI Findings (Grainger & Allison's Radiology):

• T1W: Erosions, joint space loss (damage)
• T2 fat-suppressed / STIR: Subchondral edema (active inflammation)
• Romanus lesion MRI equivalent = corner bone edema of vertebral bodies
• Costovertebral joint edema on STIR sagittal

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7. RADIOLOGY - KEY FEATURES

Plain X-ray Progression:

• Periarticular osteopenia
• Loss of SIJ definition / blurring of cortical margins
• Romanus lesion ("shiny corners") - sclerosis at anterior vertebral corners
• Squaring of vertebral bodies (erosion + reactive sclerosis)

• Syndesmophytes - thin, vertical, marginal bone outgrowths (annular ossification)
• Facet joint fusion
• SI joint erosions + sclerosis

• Bamboo spine - complete vertebral body fusion + posterior element fusion
• Complete bilateral SIJ ankylosis
• "Trolley track" sign (posterior element fusion on AP view)
• "Dagger sign" (fused interspinous ligament on AP view)

Distinguishing Syndesmophytes from Osteophytes:

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8. DIFFERENTIAL DIAGNOSIS

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9. MANAGEMENT

9a. Non-operative Treatment

• Daily stretching exercises for hip flexors and hamstrings
• Spinal extension exercises to prevent kyphosis
• Deep breathing exercises to maintain chest expansion
• Swimming is ideal (reduces axial loading)
• Sleeping supine on firm mattress with one pillow to maintain sagittal alignment
• Avoid hip flexion contractures

9b. Operative Management

Types of Spinal Osteotomy:

• Type I: Apex lumbar
• Type II: Apex thoracolumbar
• Type III: Apex thoracic
• Type IV: Apex cervical / cervicothoracic junction
• Campbell's Operative Orthopaedics 15th Ed, p. 2420-2421

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10. COMPLICATIONS & SPECIAL CONSIDERATIONS

Spinal Fractures in AS - HIGH RISK

• Osteopenic + fused spine = highly susceptible to fracture from minor trauma
• Most common site: lower cervical spine
• Often missed on plain X-rays (distorted anatomy from ossification)
• Key sign: Widened anterior disc space (hyperextension injury through disc)
• Always immobilize in position found - do NOT extend (risk of sudden neurological deficit)
• Image entire spine (associated fractures at multiple levels possible)
• CT/MRI/bone scan often needed

Atlantoaxial Instability

• 25-90% of AS patients have atlantoaxial instability
• Must be assessed pre-operatively
• Cervical spine deformity can cause disabling functional deficits

Cauda Equina Syndrome (late)

• Rare; due to arachnoid adhesions from chronic inflammation

Heterotopic Ossification after THA

• Increased risk in AS patients
• Prophylaxis: NSAIDs (indomethacin) or low-dose radiation

Andersson Lesion (Spondylodiscitis)

• Inflammatory pseudarthrosis at mobile segment in otherwise fused spine
• Mimics infection; distinguish by lack of systemic features and MRI pattern

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11. ASSESSMENT TOOLS (Orthopaedic/Rheumatology)

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12. PROGNOSIS

• After ankylosis occurs: pain often improves (burnt-out phase)
• Progressive kyphosis → fixed sagittal imbalance is the main disabling outcome
• Hip involvement → adds significantly to functional loss
• Uveitis: requires regular ophthalmology follow-up to prevent vision changes
• Renal amyloidosis: serious late complication
• Spinal fractures: frequently life-threatening

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SUMMARY TABLE

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• Campbell's Operative Orthopaedics 15th Ed (2026), pp. 2316, 2420-2421
• Grainger & Allison's Diagnostic Radiology, pp. 1119-1121
• Harrison's Principles of Internal Medicine 22E (2025), pp. 2926-2928
• Miller's Review of Orthopaedics 9th Ed, p. 63
• Firestein & Kelley's Textbook of Rheumatology (2-Volume Set)

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Physiotherapy Management of Ankylosing Spondylitis (AS / axSpA)

Evidence-Based Clinical Notes

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1. RATIONALE FOR PHYSIOTHERAPY IN AS

• Inflammation leads to progressive ankylosis - mobility must be actively maintained
• Fused spine can still develop kyphotic deformity; posture must be trained
• Drug therapy (even biologics) does not restore lost mobility - only exercise does
• Functional disability, fatigue, and quality of life are exercise-responsive outcomes
• Evidence confirms: exercise improves BASDAI, BASFI, BASMI, pain, and QoL

Key paradox (Perrotta et al., RMD Open 2021, PMID: 33547227): Biomechanical stress at entheses may theoretically promote inflammation, yet exercise programmes consistently demonstrate therapeutic benefit. The net benefit of structured exercise outweighs any theoretical entheseal risk. Exercise is recommended, not avoided.

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2. PHYSIOTHERAPY GOALS (Outcome Domains)

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3. EVIDENCE SUMMARY

Level 1 Evidence - Meta-Analyses & Systematic Reviews

RCT Level 1 Evidence

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4. PHYSIOTHERAPY ASSESSMENT

4a. Subjective Assessment

• Pain: site, character, onset, duration, radiating, aggravating/relieving factors
• Morning stiffness: duration and severity
• Functional limitations: ADL, work, recreation
• Sleep quality (pain-related)
• Fatigue level
• Psychological status (depression/anxiety common in AS)
• Smoking status (reduces exercise tolerance)
• Medications (NSAIDs, biologics)

4b. Objective Assessment (BASMI - 5 components)

Additional Objective Tests

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5. PHYSIOTHERAPY INTERVENTIONS

5a. THERAPEUTIC EXERCISE (Core Intervention)

PRINCIPLE: Exercise is ALWAYS recommended. The type, setting, and intensity should be individualized.

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A. STRETCHING & FLEXIBILITY EXERCISES

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B. STRENGTHENING EXERCISES

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C. AEROBIC EXERCISE

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D. BREATHING EXERCISES

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E. POSTURAL TRAINING

• Sleeping position: Supine on firm mattress, one flat pillow only (prevents cervical kyphosis)
• No prone sleeping initially if severe kyphosis is present
• Standing posture: Wall standing exercises - head, shoulders, buttocks touching wall
• Ergonomic advice for work (raise monitor height, avoid flexed posture)
• Avoid sitting in deep flexion for prolonged periods

• Brügger posture correction
• Mirror/wall feedback training
• Thoracic extension mobilizations before posture exercises

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F. SPINAL MOBILITY / RANGE OF MOTION EXERCISES

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5b. GROUP vs. HOME vs. SUPERVISED EXERCISE

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5c. MIND-BODY EXERCISE (Tai Chi, Yoga, Pilates, Qigong)

• BASFI improvement: MD -0.76 (P<0.00001)
• BASDAI improvement: MD -0.76 (P<0.00001)
• VAS pain: MD -0.89 (P<0.00001)
• BASMI: MD -0.44 (P=0.0006)
• QoL (ASQoL): MD -2.14 (P=0.003)
• No serious adverse events in any included study
• Tai Chi had the most pronounced pain-reduction effect vs. Qigong

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5d. AQUATIC THERAPY / HYDROTHERAPY

• Aquatic exercise superior to home exercise for pain
• Improved disease activity vs. land-based and control groups
• Improved physical function

• Water buoyancy reduces joint loading
• Warm water (32-35°C) reduces muscle spasm and pain
• Water resistance provides gentle resistance training
• Facilitates movement in patients with severe stiffness or pain

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5e. MANUAL THERAPY & ELECTROPHYSICAL AGENTS

Important: Spinal mobilization/manipulation is contraindicated in severely fused spine due to risk of chalk-stick fracture. Only gentle, graded mobilization techniques should be used in early/inflammatory disease.

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5f. PATIENT EDUCATION (Cornerstone - Equal Status with Exercise)

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6. PHYSIOTHERAPY ACROSS DISEASE STAGES

Stage 1 - Early / Active Inflammatory Phase

• Gentle ROM exercises within pain tolerance
• Hydrotherapy (warm water reduces pain)
• Deep breathing exercises
• Postural education and sleeping position advice
• NSAID timing before exercise (take 30-60 min before morning exercises)
• Avoid aggressive stretching into pain; work in pain-free range
• 10-15 min of gentle daily activity initially; build up gradually

Stage 2 - Established / Progressive Phase

• Full structured exercise programme: flexibility + strength + aerobic
• Supervised group exercise or individual physiotherapy
• Intensive chest expansion programme
• Postural correction programme
• Spinal mobility exercises (all planes)
• Aquatic therapy if land-based exercise limited

Stage 3 - Advanced / Ankylosed Phase

• Focus shifts to maintaining what is left of mobility
• Peripheral joint exercises become more important
• Fall prevention and balance training
• Respiratory physiotherapy (diaphragmatic breathing, incentive spirometry)
• Gait training; walking aids if needed
• Pre/post-operative rehabilitation if osteotomy or THA planned

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7. POST-OPERATIVE PHYSIOTHERAPY

After Total Hip Arthroplasty (THA)

• Pre-op: Assess and optimize hip ROM and strength; respiratory physiotherapy
• Day 1-2 post-op: Bed exercises, deep breathing, transfers
• Week 1-2: Gait training (walking frame → stick); hip precautions (no forced adduction/internal rotation)
• Heterotopic ossification (HO) prevention: NSAIDs (indomethacin 25mg TDS × 6 weeks) or low-dose radiation within 72 hrs
• 6-week programme: progressive ROM, strength, functional training
• HO risk is high in AS - monitor; aggressive physio of hip may worsen HO; balance needed

After Spinal Osteotomy

• Pre-op: Chest physiotherapy, breathing exercises, strengthen paravertebral muscles
• Post-op: Respiratory physiotherapy (vital capacity may be reduced postoperatively)
• Gradual mobilization in brace/orthosis
• Progressive core and postural re-education
• Gait retraining in corrected posture

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8. SPECIAL CONSIDERATIONS

Flare Management

• Do NOT stop exercise during mild-moderate flare
• Reduce intensity; shift to gentle ROM, hydrotherapy
• Swimming / pool walking ideal during flares
• Use ice/heat for symptomatic relief
• Maintain breathing exercises even during severe flares

Fatigue

• Fatigue is the most disabling symptom for many patients
• ASAS/EULAR SLR 2023 confirms non-pharmacological interventions (exercise, cognitive-behavioural approaches) moderately effective for fatigue
• Pacing strategies; sleep hygiene; aerobic exercise shown to reduce fatigue

Kinesiophobia (Fear of Movement)

• Common in AS (Ertem, 2025 PMID: 39959836)
• Graded exposure to movement; reassurance that exercise is safe
• CBT-based pain neuroscience education effective

Osteoporosis

• Common in AS (paradox: despite osteoproliferation, systemic osteoporosis occurs)
• Weight-bearing exercise (recommended as per ASAS/EULAR)
• Co-manage with rheumatologist (DEXA scan, calcium/vitamin D)

Pregnancy

• Continue low-impact exercise (swimming, walking, pelvic floor)
• Avoid prone exercises after 1st trimester
• Aquatic therapy preferred
• NSAIDs avoided in 3rd trimester; exercise even more important

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9. FREQUENCY / INTENSITY / DURATION - PRESCRIPTION SUMMARY

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10. OUTCOME MONITORING

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11. ASAS/EULAR 2022 - PHYSIOTHERAPY RECOMMENDATIONS (Key Points)

1. Non-pharmacological management should be offered to all patients at all stages
2. Education and exercise are consistently confirmed efficacious
3. Both supervised and home exercise are effective; supervised preferred for technique acquisition
4. Smoking cessation is recommended (smoking = worse outcome)
5. Physical therapy should be personalised and ongoing - not time-limited
6. Patient self-management (home exercise, lifestyle modification) is essential

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SUMMARY TABLE - Evidence-Based Physiotherapy Hierarchy in AS

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• ASAS-EULAR 2022 Recommendations - Ramiro et al., Ann Rheum Dis 2023
• ASAS/EULAR SLR 2022 - Non-pharmacological - Ortolan et al., Ann Rheum Dis 2023
• Cochrane Review: Exercise in AS - Regnaux et al., 2019
• Meta-analysis: Exercise types in AS - Boudjani et al., Disabil Rehabil 2023
• RCT: Long-term supervised exercise - van Wissen et al., Rheumatology 2025
• Meta-analysis: Mind-body exercise in axSpA - Wang et al., J Orthop Surg Res 2024
• Systematic review: Aquatic exercise in inflammatory arthritis - Medrado et al., Rheumatol Int 2022
• Physiotherapy effectiveness SR/MA in AS - Gravaldi et al., Healthcare 2022
• Paradoxical role of exercise review - Perrotta et al., RMD Open 2021
• Goldman-Cecil Medicine, Chapter on AS