Overview
Sciatica
1. Clinical Overview
Summary
Sciatica is pain radiating along the sciatic nerve distribution (L4-S3), typically from buttock to foot, usually caused by compression of a lumbar nerve root, most commonly from a prolapsed intervertebral disc. Most cases resolve with conservative management.
Key Facts
| Aspect | Detail |
|---|---|
| Definition | Leg pain radiating below the knee in a dermatomal distribution |
| Most Common Cause | L4/5 or L5/S1 disc prolapse |
| Key Sign | Positive Straight Leg Raise (SLR) |
| Prognosis | 90% resolve in 6-12 weeks |
| Red Flag | Cauda equina syndrome |
Clinical Pearls
- Leg > Back pain: Radicular pain usually exceeds back pain (back pain alone = less likely radiculopathy)
- Level vs Root: L4/5 disc compresses L5 root; L5/S1 disc compresses S1 root
- Crossed SLR: Raising unaffected leg causes affected leg pain = highly specific for disc herniation
- Cauda Equina: Urinary retention, saddle anaesthesia, bilateral symptoms = urgent MRI
2. Epidemiology
Prevalence
| Population | Prevalence |
|---|---|
| Lifetime risk | 13-40% |
| Peak age | 40-50 years |
| Gender | Slight male predominance |
Risk Factors
| Risk Factor | Association |
|---|---|
| Heavy lifting | Disc herniation |
| Prolonged sitting | Increased intradiscal pressure |
| Obesity | Increased load |
| Smoking | Disc degeneration |
| Tall stature | Increased risk |
3. Pathophysiology
Mechanism
Disc Degeneration / Annular Tear
↓
Nucleus Pulposus Herniation
↓
Compression of Nerve Root
↓
Mechanical Compression + Chemical Inflammation
↓
RADICULAR PAIN (Sciatica)
Common Levels
| Level | Root | Clinical Features |
|---|---|---|
| L3/4 | L4 | Knee extension weakness, reduced knee jerk |
| L4/5 | L5 | Great toe extension weakness (EHL), no reflex loss |
| L5/S1 | S1 | Ankle plantar flexion weakness, reduced ankle jerk |
4. Clinical Presentation
History
| Feature | Description |
|---|---|
| Pain quality | Shooting, burning, electric |
| Distribution | Buttock → posterior thigh → calf → foot |
| Below knee | Key feature of radiculopathy |
| Worse with | Sitting, coughing, sneezing, straining |
| Better with | Lying flat, walking |
| Paraesthesia | Dermatomal numbness/tingling |
Red Flag Symptoms (Cauda Equina)
| Symptom | Urgency |
|---|---|
| Urinary retention/incontinence | Emergency MRI |
| Faecal incontinence | Emergency MRI |
| Saddle anaesthesia | Emergency MRI |
| Bilateral leg weakness | Emergency MRI |
| Progressive motor weakness | Urgent referral |
5. Clinical Examination
Key Tests
| Test | Technique | Positive |
|---|---|---|
| Straight Leg Raise | Raise extended leg, hip flexion | Pain at <60° radiating below knee |
| Crossed SLR | Raise unaffected leg | Pain in affected leg (highly specific) |
| Lasègue's | Dorsiflex ankle during SLR | Increases pain |
| Femoral stretch | Prone, extend hip | L3/4 radiculopathy |
Neurological Assessment
| Level | Motor | Sensory | Reflex |
|---|---|---|---|
| L4 | Knee extension | Medial leg | Knee jerk |
| L5 | Great toe dorsiflexion (EHL) | Dorsum foot/1st web | None |
| S1 | Plantarflexion, toe walking | Lateral foot | Ankle jerk |
Cauda Equina Examination
- Perianal sensation: Saddle area
- Anal tone: Reduced in CES
- Bladder: Post-void residual (urgent catheterisation if retention)
6. Investigations
When to Image
| Indication | Test |
|---|---|
| Red flags | Urgent MRI |
| Failed conservative (>6 weeks) | MRI |
| Severe/progressive deficit | MRI |
| Surgical candidate | MRI |
MRI Findings
- Disc herniation (protrusion/extrusion/sequestration)
- Nerve root compression
- Level and laterality
Other Tests
| Test | Purpose |
|---|---|
| X-ray | Not useful for soft tissue; may exclude bony pathology |
| EMG/NCS | If diagnosis uncertain, chronic symptoms |
7. Management
Conservative (First-Line)
| Intervention | Details |
|---|---|
| Activity | Stay active (bed rest NOT recommended) |
| Analgesia | Paracetamol, NSAIDs |
| Neuropathic agents | Amitriptyline, gabapentin, pregabalin |
| Physiotherapy | Exercises, education |
| Natural history | 90% improve in 6-12 weeks |
NICE Recommendations
- Do NOT routinely offer opioids for sciatica
- Consider short course of NSAIDs (with gastroprotection if needed)
- Consider neuropathic pain medications
Second-Line
| Intervention | Notes |
|---|---|
| Epidural steroid injection | May provide short-term relief |
| Specialist referral | If no improvement by 6-8 weeks |
Surgical (if conservative fails)
| Indication | Procedure |
|---|---|
| Intractable pain >6 weeks | Microdiscectomy |
| Significant/progressive weakness | Microdiscectomy |
| Cauda equina syndrome | Emergency decompression |
8. Complications
| Complication | Notes |
|---|---|
| Chronic pain | If not resolving |
| Muscle wasting | L5/S1 radiculopathy |
| Foot drop | L5 motor deficit |
| Cauda equina syndrome | Surgical emergency |
9. Prognosis & Outcomes
| Factor | Outcome |
|---|---|
| Conservative treatment | 90% improve in 6-12 weeks |
| Post-microdiscectomy | 80-90% good/excellent outcome |
| Recurrence | ~10% at same level |
| Foot drop recovery | Variable - depends on duration |
10. Evidence & Guidelines
| Organisation | Key Points |
|---|---|
| NICE NG59 | Conservative first, imaging if red flags or considering surgery |
| Cochrane | Surgery offers faster relief but similar long-term outcome |
11. Patient / Layperson Explanation
What is sciatica? It's pain that travels from your lower back down your leg, following the path of the sciatic nerve. It usually affects just one leg and often goes below the knee.
What causes it? Usually a "slipped disc" (disc prolapse) pressing on a nerve in your spine.
Will it get better? Yes - 9 out of 10 people feel better within 6-12 weeks without surgery.
What can I do?
- Keep moving (bed rest makes it worse)
- Take regular painkillers as advised
- Consider physiotherapy
- Heat or ice packs may help
When should I see a doctor urgently?
- Difficulty controlling your bladder or bowels
- Numbness in the genital/buttock area
- Weakness in both legs
- Pain getting rapidly worse
12. References
- NICE NG59. Low back pain and sciatica. 2016.
- Ropper AH, et al. Sciatica. NEJM. 2015.
- Vroomen PC, et al. Natural course of sciatica. BMJ. 2000.