Examqo › Examqo library › Orthopedic surgery › Spine · IMLE
Lumbar disc herniation and radiculopathy (sciatica)
A lumbar disc herniation presses on a nerve root and causes pain radiating down the leg along its dermatome; most patients improve within 6–12 weeks with conservative care, and surgery (microdiscectomy) suits persistent radicular pain, progressive motor deficit or cauda equina syndrome.
Why it matters in the exam
The typical stem describes a young or middle-aged adult with back pain that began after lifting and, days later, sharp pain going below the knee, worse than the back pain, sometimes with tingling. The common levels are L4–L5 and L5–S1. A posterolateral herniation presses on the traversing root, so a herniation at L4–L5 affects the L5 root, and one at L5–S1 affects S1; a far lateral herniation presses on the exiting root, so at L4–L5 it affects L4. Questions ask you to identify the root from the examination: weak great toe extension and ankle dorsiflexion point to L5, a reduced ankle reflex and weak plantar flexion point to S1, and a reduced knee reflex with weak knee extension point to L4. The straight leg raise test (SLR) reproduces radicular pain, and the crossed straight leg raise is more specific. The natural history is good: most patients improve within weeks, and the herniated disc is sometimes even resorbed. So first-line treatment includes staying active, analgesia and physiotherapy; an epidural steroid injection can relieve acute pain. MRI is needed with warning signs, a progressive neurological deficit, or when surgery or injection is being considered. Microdiscectomy shortens the duration of pain in patients with persistent radicular pain, but long-term results are similar to conservative care.
Key points
- Common levels: L4–L5 and L5–S1.
- Posterolateral herniation affects the lower root; far lateral affects the exiting root.
- L5 — great toe extension; S1 — ankle reflex; L4 — knee reflex.
- Most patients improve within 6–12 weeks.
- Surgery — persistent pain, progressive deficit or cauda equina syndrome.
Summary table
| Root | Motor weakness | Reflex | Sensation |
|---|---|---|---|
| L4 | Knee extension (quadriceps) | Knee reflex reduced | Medial side of the leg |
| L5 | Great toe extension and ankle dorsiflexion, hip abduction | No main reflex | Dorsum of the foot and great toe |
| S1 | Ankle plantar flexion, toe walking | Ankle reflex reduced | Lateral foot and sole |
| Posterolateral herniation at L4–L5 | Affects the L5 root | — | The most common together with L5–S1 |
| Far lateral herniation at L4–L5 | Affects the L4 root | Knee reflex reduced | A confusing exam finding |
In the full version for subscribers
- A simple algorithm
- Memory aid
- Exam traps
- 5 review cards
- Enough for IMLE
The full version is open to subscribers of: Orthopedic surgery, Medical licensing exam (IMLE), Family medicine, Neurosurgery.
Subscriber? Read the full topic Plans and prices 25 free questions
Sources
- NICE Guideline NG59, 2016 (updated 2020) — Low back pain and sciatica in over 16s
- NASS Evidence-Based Clinical Guideline, 2012 — Diagnosis and Treatment of Lumbar Disc Herniation with Radiculopathy
- Campbell's Operative Orthopaedics, 14th ed. (2021) — Lower Back Pain and Disorders of Intervertebral Discs
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.