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Sciatic Nerve Palsy: Assessment & Management

Anatomy Recap

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Etiology / Causes

• Hip dislocation or fracture (posterior > anterior)
• Total hip arthroplasty (THA) — most common iatrogenic cause; 0.1–2% incidence
• Pelvic/acetabular fractures
• Penetrating injuries, gunshot wounds

• Piriformis syndrome
• Prolonged lithotomy or lateral decubitus positioning
• Gluteal compartment syndrome
• Space-occupying lesion (tumour, haematoma, abscess)

• Gluteal artery aneurysm / pseudoaneurysm

• Diabetic neuropathy (rarely isolated sciatic)
• Injection injury (intramuscular injection — upper outer quadrant misplacement)

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Assessment

History

• Onset (acute vs insidious), mechanism (trauma, surgery, injection)
• Pain distribution: buttock radiating to posterior thigh, leg, foot
• Functional deficits: difficulty walking, foot drop, inability to plantarflex
• Bladder/bowel involvement (raises concern for cauda equina — urgent)
• Diabetes, prior malignancy, anticoagulation use

Clinical Examination

Motor Testing

Sensory Testing

Reflexes

• Ankle jerk (S1): absent/reduced — tibial component
• Knee jerk: spared (femoral nerve, not sciatic)

Special Tests

• Straight leg raise (SLR): positive at <60° suggests sciatic nerve tension; sensitivity ~80%, specificity ~40% for disc herniation
• FAIR test: hip flexion, adduction, internal rotation — for piriformis syndrome
• Pace sign: weakness/pain with resisted hip abduction/external rotation — piriformis syndrome

Severity Grading (Seddon / Sunderland)

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Investigations

Electrodiagnostic Studies (EDX)

• Timing: optimally performed 3–4 weeks post-injury (allows Wallerian degeneration to complete)
• Nerve conduction studies (NCS):
  • Reduced/absent compound muscle action potential (CMAP) amplitude
  • Reduced/absent sensory nerve action potential (SNAP)
  • Sural, superficial peroneal, tibial responses
• Electromyography (EMG):
  • Fibrillations + positive sharp waves: denervation (appears at 2–4 weeks)
  • Motor unit analysis: polyphasic MUAPs on recovery
  • Test short head of biceps femoris, tibialis anterior, gastrocnemius, gluteal muscles (to localise lesion level)
  • Paraspinal muscles normal (excludes radiculopathy)
• Key distinction:
  • Sciatic palsy: abnormal EMG in short head biceps femoris + distal muscles
  • Common peroneal palsy at fibular head: normal biceps femoris (short head), normal tibial-territory muscles

Imaging

• MRI: modality of choice for soft-tissue causes (tumour, haematoma, piriformis, nerve sheath tumour); can show nerve signal change, muscle denervation oedema
• Ultrasound: dynamic assessment, especially useful for piriformis syndrome, and identifying compressive masses or nerve continuity after trauma
• X-ray / CT pelvis: for bony pathology (hip dislocation, acetabular fracture)
• MR neurography: high-resolution nerve imaging for complex cases

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Management

Acute / General Principles

• Identify and treat the underlying cause (reduce hip dislocation urgently, evacuate haematoma, stop offending injection, relieve compression)
• Prompt reduction of traumatic hip dislocation within 6 hours significantly improves prognosis

Conservative Management

Surgical Management

• Open/penetrating injuries (explore early, within days–weeks)
• Complete lesion with no EDX evidence of recovery at 3–6 months
• Identifiable compressive lesion (tumour, haematoma, pseudoaneurysm)
• Iatrogenic transection (THA, injection) — early exploration if suspected

• Neurolysis: external or internal; for scar compression
• Primary neurorrhaphy: end-to-end repair if tension-free
• Nerve grafting: sural nerve most common donor; for gaps >2–3 cm
• Nerve transfers: for proximal/severe injuries to reinnervate critical distal targets (e.g., obturator to femoral for knee stability, or tibial branch transfers)
• Tendon transfers: for established foot drop (e.g., tibialis posterior transfer through interosseous membrane) when nerve recovery is unlikely or maximal

Monitoring Recovery

• Serial clinical examination monthly
• Tinel's sign progression: advancing Tinel indicates axon regrowth (~1 mm/day)
• Repeat EDX at 3–6 months: nascent MUAPs = early reinnervation
• Upper limit for meaningful reinnervation: ~18–24 months (muscle fibrosis beyond this limits functional return)

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Prognosis

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Common Peroneal vs Sciatic Palsy: Key Differentiators

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Post-THA Sciatic Nerve Palsy (Special Consideration)

• Incidence ~0.1–2%; higher in revision THA, DDH, or leg lengthening >2.5–4 cm
• Most commonly involves the common peroneal division
• Management: flex hip and knee to reduce nerve tension; if hardware or haematoma implicated, explore early
• Prognosis: ~50% regain functional recovery; tibial division recovers better than peroneal

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Physiotherapy Assessment & Management: Sciatic Nerve Palsy

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PART 1 — PHYSIOTHERAPY ASSESSMENT

1. Subjective Assessment (History)

• Location, nature, and distribution of pain (burning, shooting, aching)
• Onset, mechanism (trauma, surgery, prolonged positioning, injection)
• Functional limitations: walking, stair climbing, rising from chair, dressing

• Prior hip pathology or surgery (THA, ORIF), lumbar spine history
• Diabetes, malignancy, peripheral vascular disease
• Bladder/bowel function (cauda equina red flag)
• Medications (neuropathic agents already trialled)

• Visual Analogue Scale (VAS) / Numeric Pain Rating Scale (NPRS)
• Oswestry Disability Index or Lower Extremity Functional Scale (LEFS)
• Neuropathic pain: DN4 questionnaire or PainDETECT

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2. Objective Assessment

Observation / Posture

• Antalgic gait, steppage gait (foot drop compensation)
• Gluteal wasting, limb length discrepancy
• Foot posture: equinovarus tendency, clawing of toes

Gait Analysis

Active & Passive Range of Motion (ROM)

• Hip: flexion, extension, abduction, IR/ER
• Knee: flexion/extension
• Ankle: dorsiflexion (key), plantarflexion, inversion, eversion
• Note contracture vs weakness limitation

Manual Muscle Testing (MMT — MRC Scale 0–5)

• 0 = No contraction
• 1 = Flicker/trace
• 2 = Movement with gravity eliminated
• 3 = Movement against gravity
• 4 = Movement against resistance (reduced)
• 5 = Normal

Sensory Assessment

Reflexes

• Ankle jerk (S1): graded 0–4+ (absent/reduced in sciatic palsy — tibial division)
• Knee jerk: expected normal (femoral nerve — useful comparison)
• Plantar response: assess for upper motor neuron signs (rule out cord involvement)

Neural Tension / Provocation Tests

Functional Tests

• Single leg stance (Romberg and dynamic)
• Timed Up and Go (TUG) test
• 10-Metre Walk Test / 6-Minute Walk Test
• Step-up/step-down test
• Heel walk (tests dorsiflexion, L4–L5) and toe walk (tests plantarflexion, S1–S2)

Palpation

• Sciatic nerve at sciatic notch, posterior thigh
• Piriformis (medial buttock between PSIS and greater trochanter)
• Tender/thickened nerve trunk
• Advancing Tinel's sign (percussion along nerve — tingling distally = axon regeneration front)

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3. Physiotherapy Problem List (Example)

• Foot drop — risk of falls, tripping
• Ankle dorsiflexion weakness (MRC 2/5)
• Reduced sensation — dorsum foot and sole
• Proprioceptive deficit — ankle and hallux
• Reduced ankle ROM — tight Achilles/posterior capsule
• Impaired balance — single leg stance <5 seconds
• Altered gait — steppage pattern
• Neuropathic pain — VAS 6/10
• Fear of falling — reduced confidence (assess with Falls Efficacy Scale)

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PART 2 — PHYSIOTHERAPY MANAGEMENT

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Phase 1 — Acute / Early (0–6 weeks)

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Phase 2 — Subacute / Re-innervation (6 weeks – 6 months)

Motor Re-education

Sensory Re-education

• Early phase: graded sensory stimulation — cotton, brush, textures; vibration (tuning fork, vibrating tool)
• Late phase: texture discrimination, object identification (stereognosis), balance on varied surfaces
• Mirror therapy: useful adjunct for cortical remapping in chronic cases
• Proprioceptive retraining: wobble board, foam pad, BOSU ball progressions

Neural Mobilisation (Progression)

• Sliders: hip flexion with knee extension alternated with hip extension with knee flexion — moves nerve without tension
• Tensioners: used cautiously once acute inflammation subsides; SLR with ankle dorsiflexion
• Frequency: daily, within symptom-free range; avoid aggravating neurogenic pain

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Phase 3 — Functional / Late Rehabilitation (6 months+)

Gait Retraining

• AFO weaning: as dorsiflexion recovers (MRC ≥3), trial dynamic AFO → no AFO with supervision
• Treadmill training: visual and verbal feedback; body-weight support treadmill (BWSTT) if significant weakness
• Obstacle course training, stair training, ramp walking
• Address compensatory strategies (steppage, circumduction) with mirror/video feedback

Progressive Strengthening

• Resistance progression: gravity-eliminated → against gravity → resistance bands → free weights → functional
• Eccentric loading for hamstrings (Nordic curls, Romanian deadlift)
• Single-leg press, single-leg calf raise
• Sport/occupation-specific loading

Balance & Proprioception

• Single leg stance: firm → foam → eyes closed progressions
• Perturbation training
• Functional reach test — target improvement
• Dual-task balance training (balance + cognitive task)

Hydrotherapy

• Buoyancy reduces weight-bearing demands
• Warm water facilitates muscle relaxation and pain reduction
• Walking in water: earlier active gait training pre-land ambulation
• Resistance of water for strengthening as function improves

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Pain Management (Across All Phases)

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Orthotic & Assistive Devices

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Functional Electrical Stimulation (FES)

• NMES (Neuromuscular Electrical Stimulation): denervated muscle — direct muscle stimulation (low frequency, longer pulse width 200–1000 µs)
• FES: stimulates intact nerve to trigger dorsiflexion during swing phase (e.g. WalkAide, Bioness L300)
  • Best evidence for incomplete lesions where some neural continuity remains
  • Maintains muscle bulk, prevents fibrotic change, re-educates motor pattern
• Electrode placement: tibialis anterior (peroneal nerve at fibular head)

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Psychological & Holistic Considerations

• Address fear-avoidance beliefs (Tampa Scale of Kinesiophobia)
• Goal-setting using SMART goals; patient-centred approach
• Vocational rehabilitation: modified duties, workplace ergonomic assessment
• Falls prevention programme for high-risk patients (elderly, bilateral involvement)
• Support groups / peer connection for long-term neurological conditions

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Monitoring Progress — Outcome Measures Summary

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Red Flags During Physiotherapy — Refer / Escalate

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Summary: Physiotherapy Goal Progression

Phase 1 (0–6 wks):   Protect → prevent contracture → pain control → patient education
Phase 2 (6wk–6mo):   Motor re-education → sensory retraining → neural mobilisation → gait training
Phase 3 (6mo+):      Functional strength → balance → gait normalisation → return to activity