Orthopaedics
General Practice
Rheumatology
High Evidence

Low Back Pain and Sciatica

Updated 2026-01-04
5 min read

Low Back Pain and Sciatica

1. Clinical Overview

Summary

Low Back Pain (LBP) is the leading cause of disability worldwide. 85% of cases are "Non-specific Mechanical LBP" where no specific anatomical cause (like cancer or infection) is found.

Management involves triage into three categories:

  1. Serious Pathology (Red Flags): less than 1%. Cancer, Infection, Fracture, Cauda Equina.
  2. Radicular Pain (Sciatica): 5-10%. Nerve root compression. Sharp, shooting leg pain.
  3. Non-specific Mechanical LBP: 90%. Muscle strain/Degeneration.

The golden rule is diagnostic triage to rule out Red Flags. If Red Flags are absent, imaging (MRI/X-Ray) is NOT indicated and can be harmful (VOMIT - Victim of Modern Imaging Technology). Management focuses on keeping active and avoiding bed rest.

Key Facts

  • Prevalence: 80% of adults will experience LBP.
  • Prognosis: 90% of acute attacks resolve within 6 weeks regardless of treatment.
  • Sciatica: 90% of disc herniations resolve spontaneously via resorption (macrophage phagocytosis) within 3-4 months.
  • Cauda Equina Syndrome (CES): A surgical emergency. The most common cause of high-value litigation in spinal surgery.

Clinical Pearls

The "Crossed SLR" Pearl: While a positive Straight Leg Raise (pain in affected leg when lifted) is sensitive for sciatica, a Positive Crossed SLR (pain in the affected leg when the good leg is lifted) is highly specific (90%) for a large disc herniation.

The "Retention" Pearl: In Cauda Equina Syndrome, Painless Urinary Retention with overflow incontinence is the classic sign. If a patient with back pain cannot feel themselves voiding, it is an emergency.

The "Yellow Flag" Pearl: Psychosocial factors (Depression, Job dissatisfaction, Fear avoidance) are stronger predictors of chronicity than MRI findings.

2. Epidemiology

Risk Factors

1. Physical

  • Heavy lifting (manual handling).
  • Sedentary lifestyle / Obesity.
  • Smoking (Decreases disc nutrition).

2. Psychosocial (Yellow Flags)

  • Depression / Anxiety.
  • "Catastrophising" (Believing pain = damage).
  • Pending litigation / Compensation claims.

3. Age

  • Young (20-40): Disc Herniation, Ankylosing Spondylitis.
  • Old (> 60): Spinal Stenosis, Osteoporotic Fracture, Metastases.

3. Pathophysiology

Mechanical LBP

  • Strain of paraspinal muscles.
  • Facet Joint Arthropathy (Osteoarthritis of the zygapophyseal joints).
  • Degenerative Disc Disease (Loss of disc height / water content).

Radiculopathy (Sciatica)

  • Herniated Nucleus Pulposus (HNP): The soft inner gel (Nucleus) bursts through the tough outer ring (Annulus Fibrosus).
  • Chemical Radiculitis: The nucleus material is highly inflammatory (low pH, high Phospholipase A2). It irritates the nerve root.
  • Compression: Physical pressure causes numbness/weakness.

Spinal Stenosis

  • Narrowing of the spinal canal due to:
    1. Disc bulging anteriorly.
    2. Facet Joint hypertrophy posteriorly.
    3. Ligamentum Flavum buckling.
  • Causes Neurogenic Claudication (Ischaemia of nerve roots on walking).

Spondylolisthesis (The "Slip")

  • Anterior slippage of one vertebra on another (usually L5 on S1).
  • Spondylolysis: Defect in the pars interarticularis ("Scotty Dog" collar fracture on Oblique X-Ray). Common in gymnasts/cricketers.
  • Degenerative: Slippage due to facet failure in elderly.

4. Triage: The Red Flags

(CRITICAL SECTION)

Cauda Equina Syndrome (CES)

Compression of the sacral nerve roots (L4-S4).

  • Symptoms:
    • Bilateral Sciatica.
    • Saddle Anaesthesia (Numb bum/perineum).
    • Urinary Retention / Incontinence.
    • Faecal Incontinence (loss of anal tone).
    • Erectile Dysfunction.
  • Action: Emergency MRI Whole Spine.

Spinal Infection (Discitis/Osteomyelitis)

  • Risk Factors: IVDU, Recent Surgery, Immunosuppression.
  • Symptoms: Fever, Night sweats, Constant severe pain unaffected by rest.

Spinal Malignancy (Metastases)

  • Primary: Breast, Bronchus (Lung), Prostate, Kidney, Thyroid (Lead Kettle - PB KTL).
  • Symptoms: Unrelenting night pain, Weight loss, History of Ca.

Spinal Fracture

  • Major Trauma: Car crash.
  • Minor Trauma: Osteoporosis (Sneezing/Lifting a plant pot).

5. Clinical Presentation (By Level)

(Localising the Lesion)

L4 Nerve Root (L3/L4 Disc)

  • Motor: Weakness of Knee Extension (Quads) / Ankle Dorsiflexion (Tib Ant).
  • Reflex: Knee Jerk reduced.
  • Sensory: Medial Shin / Knee.
  • Pain: Anterior Thigh.

L5 Nerve Root (L4/L5 Disc)

Most Common.

  • Motor: Weakness of Big Toe Extension (EHL). No reflex loss.
  • Reflex: None.
  • Sensory: Dorsum of foot / Big Toe web space.
  • Pain: Lateral Thigh / Lateral Calf.

S1 Nerve Root (L5/S1 Disc)

Second Most Common.

  • Motor: Weakness of Plantar Flexion (Calf raise) / Eversion.
  • Reflex: Ankle Jerk reduced.
  • Sensory: Lateral Foot / Sole / Little Toe.
  • Pain: Posterior Thigh / Calf / Heel.

6. Management: Non-Specific LBP

(NICE NG59)

1. Reassurance & Activation

  • Do not advise Bed Rest. It promotes stiffness and disability.
  • Stay Active: Carry on with normal activities as pain allows.
  • Explain favourable prognosis.

2. Pharmacological

  • First Line: NSAIDs (Naproxen/Ibuprofen) + PPI. Lowest dose.
  • Do NOT use: Paracetamol monotherapy (ineffective). Opioids (avoid if possible). Gabapentinoids (for sciatica only).

3. Physical Therapy

  • Manual therapy (Massage/Mobilisation).
  • Group Exercise programmes (Yoga/Pilates).

4. Psychological

  • CBT (Cognitive Behavioural Therapy) for chronic pain.
  • STarT Back Tool: Screening tool to stratify risk of chronicity.

7. Management: Sciatica (Radiculopathy)

(Stepwise Approach)

1. Conservative (6-12 weeks)

  • Wait for resorption.
  • Neuropathic Pain Meds: Amitriptyline, Gabapentin, Pregabalin (Check NICE guidelines).

2. Spinal Injections

  • Transforaminal Epidural Steroid Injection (Nerve Root Block).
  • Targeted delivery of steroid to the inflamed nerve. Potent anti-inflammatory.
  • Does not "cure" the disc, but buys time for resorption.

3. Surgery (Microdiscectomy)

  • Indication: Failure of conservative care (6-12 weeks) with severe pain. Or Progressive neurological deficit (Foot drop).
  • Procedure: Small incision. Remove the fragment pressing on the nerve.
  • Outcome: Excellent for Leg Pain (90% relief). Unpredictable for Back Pain.

8. Management: Spinal Stenosis

(Neurogenic Claudication)

Presentation

  • Elderly patient.
  • "Legs feel heavy/tired" after walking 100 yards.
  • Relieved by Flexion (Leaning on a shopping trolley - "Shopping Trolley Sign"). Flexion opens the canal. Extension (walking downhill) closes it.

Management

  1. Conservative: Physio, Analgesia.
  2. Epidural Steroids: Variable Benefit.
  3. Surgery: Lumber Decompression (Laminectomy).
    • Remove the spinous process and lamina to open the canal.
    • High success rate for leg symptoms.

9. Cauda Equina Syndrome (CES) - Deep Dive

(The Medico-Legal Minefield)

Classification

  1. CES-I (Incomplete):
    • Subjective urinary changes (loss of desire to void, poor stream).
    • Saddle sensory change.
    • Action: Urgent decompression may prevent permanent damage.
  2. CES-R (Retention):
    • Painless urinary retention with overflow incontinence.
    • Established sphincteric paralysis.
    • Action: Decompression less likely to restore bladder function. (Damage is done).

Emergency Protocol

  • PR Exam: Check anal tone and sensation (perianal).
  • Bladder Scan: > 400ml indicated retention.
  • MRI: Whole Spine Emergency.
  • Surgery: Emergency Decompression (Discectomy/Laminectomy) day or night.

10. Complications of Surgery

(Informed Consent)

General

  • Infection: 1-2%. Discitis is rare but devastating (months of pain).
  • Dural Tear: 5%. Leakage of CSF. Requires patch repair. Can cause spinal headaches.

Specific

  • Nerve Root Injury: Worsening of foot drop / numbness. (1%).
  • Recurrent Herniation: 5-10%. The disc can herniate again at the same level.
  • Fibrosis/Scarring: Epidural fibrosis causing persistent leg pain.

11. Chronic Pain Management

(When Cure is Not Possible)

The Biopsychosocial Model

  • Pain Management Programmes (PMP): Group therapy combining physio and psychology. Goal is "Coping", not "Curing".
  • Opioid Reduction: Long term opioids cause Hyperalgesia (OIH) and endocrine suppression. Weaning is a priority.
  • Spinal Cord Stimulation (SCS): Implantable device for Failed Back Surgery Syndrome (FBSS).

12. Evidence & Guidelines

Guidelines

  1. NICE NG59 (2016): Low back pain and sciatica in over 16s.
    • Emphasis on "Self Management" and "Exercise".
    • Discourages routine imaging.
    • Discourages Acupuncture / Traction / Ultrasound therapy.
  2. NASS Guidelines: Spinal Stenosis management.

Key Trials

  • SPORT Trial: Compared surgery vs conservative for Disc Herniation. Showed earlier relief with surgery, but no difference at 2 years (crossover was high).
  • VOMIT Studies: "Victims of Modern Imaging Technology". Showing asymptomatic people have "herniated discs" on MRI.

13. Patient Explanation

"Do I need an MRI?"

Usually, no. An MRI is a picture of anatomy, but it doesn't show pain. 50% of 50-year-olds have "slipped discs" on MRI but have no pain. Seeing it might make you worry unnecessarily. We treat the person, not the picture.

"Is my back crumbling?"

No. Your spine is incredibly strong. "Degeneration" is like "grey hair of the spine". It is normal ageing, not a disease. Motion is Lotion. Resting makes it rust.

"When should I go to A&E?"

If you cannot pee (and your bladder feels full), or you wet yourself, or you go numb around your back passage. These are signs the main nerve bundle is squashed.

14. References

  1. National Institute for Health and Care Excellence (NICE). Low back pain and sciatica in over 16 s: assessment and management. NICE Guideline [NG59]. Published: 30 November 2016.

  2. Weinstein JN et al (SPORT). Surgical vs nonoperative treatment for lumbar disk herniation: the Spine Patient Outcomes Research Trial (SPORT): a randomized trial. JAMA. 2006 Nov 22;296(20):2441-50. PMID: 17119140

  3. Deyo RA et al. Overtreating chronic back pain: time to back off? J Am Board Fam Med. 2009 Jan-Feb;22(1):62-8. PMID: 19124635

15. Examination Focus

Common Exam Questions

  1. "Patient with Foot Drop. Which nerve root?"
    • Answer: L5. (Supplies Tibialis Anterior / EHL).
  2. "Patient cannot walk on Tiptoes. Which nerve root?"
    • Answer: S1. (Gastrocnemius / Plantar flexion).
  3. "Shopping Trolley Sign?"
    • Answer: Spinal Stenosis. (Flexion improves symptoms).
  4. "Dermatome for Big Toe?"
    • Answer: L5.

Viva Points

  • Cauda Equina vs Conus Medullaris:
    • CES: LMN signs (flaccid bladder/legs). Asymmetric.
    • Conus: UMN signs (maybe spasticity). Symmetric.
  • Waddell's Signs: Non-organic signs of back pain (suggesting psychosocial component). e.g. Superficial tenderness, Distraction, Overreaction.

Last Reviewed: 2026-01-04 | MedVellum Editorial Team