Musculoskeletal

Low Back Pain and Red Flags

Most low back pain is non-specific and improves with activity and self-management, but every assessment must identify cauda equina syndrome, fracture, infection, malignancy and inflammatory disease that require a different pathway.

In a nutshell

Most low back pain is non-specific and does not need imaging. At every presentation, look for cauda equina syndrome, fracture, infection, malignancy and inflammatory disease. Encourage normal activity, self-management and exercise; use NSAIDs cautiously and avoid paracetamol alone, chronic opioids and ineffective medicines for sciatica. New bladder or bowel dysfunction, saddle sensory change or progressive neurological deficit requires emergency MRI and spinal assessment.

Classic presentation

A person with axial low back pain after ordinary activity, no red flags or neurological deficit and preserved function, compared with a person who develops new urinary retention and saddle numbness requiring emergency cauda-equina assessment.

Key points

Do not try to identify an exact painful disc or facet in uncomplicated pain; first exclude serious pathology and assess function and psychosocial risk.
Do not request routine imaging in non-specialist care for uncomplicated low back pain or sciatica; specialist imaging is justified only if it is likely to change management.
Cauda equina red flags include new bladder or bowel dysfunction, altered saddle sensation, sexual dysfunction and bilateral or progressive neurological symptoms; arrange emergency MRI and spinal referral.
Encourage normal activity, self-management and an exercise programme; avoid bed rest and passive over-medicalisation.
For low back pain, consider an NSAID only after GI, renal, hepatic and cardiovascular risk assessment, at the lowest effective dose for the shortest time; do not offer paracetamol alone.
For sciatica, do not offer gabapentinoids, other antiepileptics, oral corticosteroids or benzodiazepines; NSAID benefit is limited and toxicity must be considered.
Manual therapy belongs in a package with exercise, with or without psychological therapy; consider specialist epidural or decompression only in selected cases.
Reassess when pain, function or neurological symptoms worsen or recovery is not following the expected course.

First-line investigation

Structured red-flag history, functional assessment and neurological examination, with emergency MRI only when cauda equina or another serious cause is suspected.

Management

Exclude cauda equina and serious pathology

Ask about bladder, bowel, saddle and sexual function, bilateral or progressive weakness, trauma, fever, cancer, infection risk and inflammatory features; send suspected cauda equina for emergency MRI and spinal assessment.^1,2,3

Support normal activity and recovery

For non-specific pain, provide reassurance and self-management advice, encourage normal activities and consider a group exercise programme or risk-stratified support.^1,4

Prescribe analgesia cautiously

Consider an NSAID after GI, renal, hepatic and cardiovascular assessment at the lowest effective dose for the shortest time; do not offer paracetamol alone or chronic opioids.^1,5

Apply sciatica medicine cautions

Do not offer gabapentinoids, other antiepileptics, oral corticosteroids or benzodiazepines for sciatica; use NSAIDs only with careful risk-benefit assessment.^1,5

Refer selected persistent or severe sciatica

Use exercise-based rehabilitation and consider specialist epidural injection for acute severe sciatica or decompression when concordant imaging follows unsuccessful non-surgical treatment.¹

Safety-net and reassess

Give explicit emergency advice for bladder, bowel, saddle, sexual or progressive neurological symptoms and review any change in pattern, function or expected recovery.^1,2,3

Exam traps

New urinary retention or altered bladder sensation with saddle sensory change is an emergency even if leg power and reflexes are initially preserved.
Routine imaging is not a substitute for clinical assessment and often finds asymptomatic degenerative changes.
Do not offer paracetamol alone, gabapentinoids, oral steroids or benzodiazepines for sciatica.
Do not use opioids for chronic low back pain; if a weak opioid is considered for acute low back pain, an NSAID must be contraindicated, not tolerated or ineffective.
Manual therapy should be part of an exercise-based package, not a stand-alone passive treatment.
Epidural injection and decompression are specialist options for selected sciatica, not treatment for uncomplicated axial pain.

Illustrations

Lumbar spine anatomyDiagram of the lumbar vertebrae, discs, facet joints, nerve roots and cauda equina, labelled without implying that one visible structure explains every episode of non-specific pain.PassFinals · original

Cauda equina compressionSagittal MRI image showing a compressive lesion affecting the cauda equina, paired with the clinical red flags that require emergency assessment.Jing Jing Chan and Jen Jen Oh, Wikimedia Commons · CC-BY-4.0

Red flag screening pathwayFlow diagram showing the assessment branches for cauda equina, fracture, infection, malignancy, inflammatory disease and uncomplicated low back pain.PassFinals · original

Key sources

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.