Synopsis
Localise lumbar nerve-root dysfunction, recognise cauda equina syndrome without delay, use imaging only when it changes care, and sequence evidence-based non-operative and surgical options.
- Lumbar radiculopathy is nerve-root dysfunction: leg pain usually follows a dermatomal tendency and may be accompanied by root-specific sensory loss, weakness or depressed reflexes; common MRI abnormalities are not automatically causal.
- A posterolateral L4–5 disc usually affects the traversing L5 root, while L5–S1 commonly affects S1; far-lateral or foraminal discs more often affect the exiting root.
- New bladder, bowel or sexual disturbance, or new perineal numbness, with severe radiating low-back pain triggers immediate referral for cauda equina assessment under NICE NG127—do not wait for every classic feature.
Key red flags
New urinary retention, impaired urinary sensation, overflow incontinence, faecal incontinence, loss of sexual function or new saddle/perineal numbness with radiating low-back pain requires immediate cauda equina assessment.
Rapidly progressive or severe motor deficit, especially bilateral weakness, foot drop or loss of walking ability, requires urgent spinal review rather than routine conservative follow-up.
Fever, immunosuppression, injecting-drug use, recent bacteraemia or spinal procedure raises spinal infection; constant night pain, weight loss or cancer history raises malignant compression.
Significant trauma, osteoporosis or long-term glucocorticoids raises fracture; a pulsatile abdominal mass, collapse or vascular risk can indicate a non-spinal emergency.
Painful weakness with upper-motor-neuron signs, a sensory level or arm involvement is not explained by a single lumbar root and should prompt reconsideration of cord or brain disease.
A painless progressive deficit, systemic neuropathy pattern or symptoms not following a root distribution should not be forced into a disc diagnosis merely because MRI shows degeneration.
Ask explicitly about urinary sensation, initiation and retention, continence, bowel control, sexual function and altered saddle sensation. New dysfunction with severe radiating low-back pain requires immediate pathway referral even without bilateral sciatica.
Repeat power testing when pain is controlled and compare sides. A new or worsening objective motor deficit changes urgency and should be discussed promptly with spinal services.
Investigation priorities
Localise the root, quantify weakness and identify cauda equina or cord features.
Management branches
Leg-dominant radicular pain or deficit persists without cauda equina or another emergency.
- Explain the likely course, support normal activity and work where possible, and offer a tailored exercise-based programme with review of function and neurological change.
- If pain or function remains substantially impaired, arrange specialist assessment; obtain imaging only when the result is likely to change management, and require clinical–radiological concordance.