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This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
Key points
- Sciatica = radicular pain radiating below the knee in a dermatomal distribution (L4, L5, or S1 most common)
- LEG pain is typically WORSE than back pain (if back pain predominates, think non-specific LBP)
- Most common levels: L4/L5 (compresses L5 root) and L5/S1 (compresses S1 root)
- Conservative management first: 80% resolve within 6–12 weeks without surgery
- Surgical referral (microdiscectomy) if persistent severe sciatica >6 weeks despite conservative treatment, or progressive neurological deficit
Overview
Lumbar disc prolapse (herniation) occurs when the nucleus pulposus herniates through the annulus fibrosus, compressing an adjacent nerve root. The most commonly affected levels are L4/L5 (L5 nerve root) and L5/S1 (S1 nerve root). A posterolateral disc prolapse compresses the traversing nerve root (e.g. L4/L5 disc compresses L5 root). A far lateral disc prolapse compresses the exiting root at the same level. Sciatica describes radicular pain in the distribution of the sciatic nerve (L4-S1), typically radiating from buttock down the posterior/lateral leg to the foot. The majority (~80%) of disc prolapses resolve with conservative management as the herniated material resorbs.
Epidemiology
Sciatica affects approximately 5% of people with low back pain. Peak incidence is 30–50 years. Risk factors include heavy lifting, prolonged sitting, obesity, smoking, and occupational vibration exposure. It is more common in men.
Clinical Features
Symptoms
Radicular leg pain: sharp, shooting, radiating below the knee in a dermatomal pattern. Worse than back pain
Numbness or paraesthesiae in the affected dermatome
Weakness: foot drop (L5 — ankle dorsiflexion), inability to tiptoe (S1 — plantarflexion)
Pain worse with sitting, bending, coughing, sneezing (increases intradiscal pressure)
Bilateral leg symptoms, saddle anaesthesia, bladder/bowel dysfunction = CAUDA EQUINA — emergency
Signs
Positive straight leg raise (SLR): reproduction of radicular pain at <60° of passive leg raise (sensitive for L5/S1 root compression)
Crossed SLR positive: raising the UNAFFECTED leg reproduces pain in the AFFECTED leg (highly specific)
L4 root: weak knee extension, reduced knee jerk, medial leg/foot numbness
L5 root: weak ankle dorsiflexion (foot drop), weak EHL, numbness dorsum of foot. No reflex change (L5 has no easily testable reflex)
S1 root: weak ankle plantarflexion, reduced ankle jerk, numbness lateral foot/sole
Investigations
First-line
Clinical diagnosisNo routine investigations if typical sciatica without red flags. Most cases resolve conservatively — imaging is only needed if considering surgery or red flags present
Second-line
MRI lumbar spineInvestigation of choice if: symptoms persist >6 weeks and surgery being considered, progressive neurological deficit, or red flags (cauda equina, cancer, infection)
Specialist
Nerve conduction studies/EMGIf diagnostic uncertainty — differentiates radiculopathy from peripheral neuropathy or plexopathy
1
Conservative management (first-line)
- Reassurance: ~80% resolve within 6–12 weeks without surgery
- Stay active, avoid bed rest
- Analgesia: NSAIDs (first-line), neuropathic pain agents (gabapentin, pregabalin) may be considered for radicular pain
- Exercise therapy and physiotherapy
- Do NOT offer opioids for chronic sciatica (NICE)
2
Interventional
- Epidural steroid injection: may provide short-term relief for radicular pain. Not recommended routinely by NICE for LBP but may be considered for sciatica
3
Surgical referral
- Consider referral for microdiscectomy if: sciatica persists >6 weeks despite conservative treatment AND MRI confirms concordant disc prolapse
- Urgent referral: progressive neurological deficit (worsening weakness)
- Emergency referral: cauda equina syndrome (bilateral symptoms, saddle anaesthesia, bladder/bowel dysfunction)
Complications
- Cauda equina syndrome: Large central disc prolapse — bilateral symptoms, saddle anaesthesia, urinary retention. SURGICAL EMERGENCY
- Chronic sciatica: ~20% have persistent symptoms beyond 12 weeks
- Foot drop: L5 root compression — may require AFO (ankle-foot orthosis)
- Recurrent disc prolapse: ~5–10% after microdiscectomy
UKMLA Exam Tips
- 1L5 root: foot drop (weak dorsiflexion), numbness dorsum of foot, NO reflex change
- 2S1 root: weak plantarflexion (cannot tiptoe), reduced ankle jerk, numbness sole/lateral foot
- 3L4 root: weak knee extension, reduced knee jerk, medial leg numbness
- 4Straight leg raise: pain at <60° = positive. Crossed SLR positive = highly specific for disc prolapse
- 5Most disc prolapses resolve conservatively (~80%) — surgery only if persistent despite conservative Rx or progressive neurology
- 6Bilateral sciatica + saddle anaesthesia + bladder dysfunction = cauda equina EMERGENCY
- 7Most common levels: L4/L5 disc → L5 root, L5/S1 disc → S1 root
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