Lower Back Pain and Sciatica

Introduction

Low back pain is pain, muscle tension or stiffness localised below the costal margin and above the inferior gluteal folds, with or without leg pain. It is one of the commonest reasons for people to consult a GP in the UK, and the majority of adults will experience at least one episode during their lifetime. The World Health Organization estimated that 619 million people were living with low back pain globally in 2020, making it the single leading cause of years lived with disability worldwide, with the number of cases projected to rise to 843 million by 2050 as populations age.⁴

Despite that enormous burden, around 90% of presentations are non-specific: there is no identifiable structural or systemic cause, the episode is self-limiting, and the vast majority of patients improve substantially within a few weeks whatever is done. Serious underlying pathology accounts for well under 1% of primary care presentations.

The clinical skill being examined, therefore, is not diagnosing the pain. It is the disciplined, repeatable process of screening every presentation for the small minority who have cauda equina syndrome, a vertebral fracture, spinal infection, malignancy or inflammatory disease - while resisting the temptation to over-investigate and over-medicalise the rest. NICE NG59 sets out the UK framework for this in people aged 16 and over, and is the guideline your answers should follow.¹

Classification

The single most useful thing you can do with a patient presenting with back pain is place them into one of three groups, because each carries a completely different pathway. This triage is done on history and examination alone, and takes only a few minutes.

1. Non-specific (mechanical) low back pain - the large majority. Pain arising from the muscles, ligaments, facet joints and discs of the lumbar spine without an identifiable specific pathology. It varies with posture and activity and has no neurological deficit.
2. Sciatica (radicular pain, or radiculopathy) - pain arising from irritation or compression of a lumbosacral nerve root, most often by an intervertebral disc prolapse. Leg pain dominates, radiates below the knee in a dermatomal pattern, and may be accompanied by objective sensory, motor or reflex changes.
3. Specific spinal pathology - the small but critical group in whom the back pain is a symptom of something else: cauda equina syndrome, vertebral fracture, spinal infection (discitis, vertebral osteomyelitis, epidural abscess), spinal malignancy (usually metastatic), or inflammatory disease such as axial spondyloarthritis.

It is worth being precise about terminology. Radicular pain is the nerve root pain itself; radiculopathy strictly means an objective neurological deficit in that root distribution (weakness, sensory loss or a lost reflex). Sciatica is the everyday term used for both, and NICE uses it that way in NG59. Note also that referred pain into the buttock or posterior thigh is common in non-specific back pain and does not make it sciatica - the distinguishing feature is a clear dermatomal radiation below the knee.

Roughly 5-10% of people with low back pain have sciatica. Around 90% of sciatica is caused by lumbar disc herniation, most commonly at L4/5 and L5/S1, with lumbar spinal stenosis, spondylolisthesis and foraminal narrowing accounting for most of the remainder.

Risk factors

Risk factors for developing an episode, and for that episode becoming persistent and disabling, overlap but are not identical. The psychosocial factors in the second half of this list are the stronger predictors of chronicity, which is why they are asked about routinely and formalised in the STarT Back Tool.

• Previous episodes of back pain - the strongest single predictor of a further episode
• Occupational factors - heavy manual handling, repetitive lifting and twisting, prolonged sitting or driving, whole-body vibration
• Obesity, physical inactivity and poor general fitness
• Smoking
• Increasing age, and coexisting osteoporosis in older patients
• Psychological distress - anxiety, depression, and catastrophising about the pain
• Fear-avoidance beliefs - the belief that activity will cause further damage, leading to withdrawal from movement and progressive deconditioning
• Job dissatisfaction, low social support, and ongoing compensation or litigation claims

Clinical features

Non-specific (mechanical) low back pain

The defining characteristic is that the pain varies with posture and activity. It is typically worse with prolonged sitting, standing still or bending, often eases with gentle movement and changes of position, and is relieved by lying down. Onset may follow an unaccustomed activity such as lifting, or may be entirely unexplained. Morning stiffness, if present, lasts minutes rather than the prolonged stiffness of inflammatory disease.

Pain is felt across the lumbar region and may radiate into the buttock or posterior thigh as somatic referred pain - a dull, diffuse ache without a clear dermatomal boundary that characteristically stops above the knee. Examination shows a variable reduction in lumbar range of movement and paraspinal muscle tenderness or spasm, but the neurological examination is normal and the straight leg raise does not reproduce radicular pain.

Sciatica

In sciatica the leg pain is usually worse than the back pain, which is a useful discriminator from mechanical back pain with referred buttock ache. The pain is characteristically unilateral, sharp, burning or electric in quality, and radiates from the buttock down the posterior or lateral leg below the knee, often to the foot, in a distribution that follows a single dermatome.

• Paraesthesia or numbness in the same dermatomal distribution as the pain
• Weakness in the corresponding myotome - most often ankle or great toe dorsiflexion (L5) or plantarflexion (S1)
• Loss of the corresponding reflex - knee (L3/L4) or ankle (S1)
• Aggravation by anything that increases nerve root tension or intraspinal pressure - coughing, sneezing, straining, sitting, and forward flexion
• A positive straight leg raise on the affected side
• An antalgic posture or gait, sometimes with a sciatic list (lateral trunk shift away from the side of the pain)

The straight leg raise

With the patient supine and relaxed, the examiner passively raises the extended leg by the heel with the knee kept straight, which progressively tensions the sciatic nerve and the L5 and S1 roots. The test is positive when it reproduces the patient's own radicular pain radiating below the knee, typically between 30° and 70° of elevation. Pain felt only in the back, or simple hamstring tightness, is not a positive test - a distinction candidates frequently get wrong.

The finding can be confirmed with sensitising manoeuvres: dorsiflexing the ankle at the point of pain (Bragard's sign) or asking the patient to flex the neck should exacerbate it, whereas musculoskeletal hamstring pain will not change. The crossed straight leg raise, in which raising the unaffected leg reproduces pain in the affected leg, is much less sensitive but considerably more specific for a disc herniation. For the upper lumbar roots (L2-L4) the equivalent is the femoral stretch test: with the patient prone, flexing the knee and extending the hip reproduces anterior thigh pain.

Higher roots occasionally appear in questions: L3 gives anterior thigh sensory loss, weak knee extension and a reduced knee jerk, and is tested with the femoral stretch rather than the straight leg raise.

Lumbar spinal stenosis and neurogenic claudication

Degenerative narrowing of the central canal or lateral recesses in older patients produces a distinct syndrome: bilateral buttock and leg pain, heaviness or paraesthesia brought on by walking and by standing upright, and relieved by sitting or leaning forward. Patients often describe walking further when pushing a shopping trolley or leaning on a bicycle - the so-called shopping trolley sign - because lumbar flexion increases the canal diameter. Distinguishing it from vascular claudication is a classic exam comparison.

Red flags

Red flags are features from the history and examination that raise the possibility of specific spinal pathology and change the pathway from conservative management to investigation and referral. They should be screened for at every assessment, not just the first, because a patient reviewed for persistent pain may have developed new features since.

The most important distinction to make is one of urgency. Cauda equina features require same-day emergency referral. The remaining red flags require urgent assessment and imaging - typically within days, and immediately if there is a progressive neurological deficit or the patient is systemically unwell - but not usually within the same hour.

Assessment

The purpose of the assessment is threefold: exclude specific pathology, identify whether the pain is radicular, and gauge the risk of the episode becoming persistent and disabling. NICE explicitly frames this as risk stratification rather than diagnosis, because for the large non-specific group there is no diagnosis to be made beyond that label.¹

History

• Site, radiation and character - and specifically whether the leg pain goes below the knee and follows a dermatome
• Which is worse, the back or the leg? - leg-dominant pain points to a radicular cause
• Onset, duration and course - sudden versus insidious, first episode versus recurrent, and whether it is improving or progressing
• Aggravating and relieving factors - a mechanical pattern that varies with posture and activity is reassuring; unremitting pain that is worse at rest or at night is not
• A structured red flag screen, including the cauda equina questions asked explicitly
• Neurological symptoms - weakness, numbness, paraesthesia, and any change in gait or falls
• Systemic enquiry - weight loss, fever, night sweats, previous cancer, and features of inflammatory disease such as psoriasis, uveitis or inflammatory bowel disease
• Yellow flags - beliefs about the pain and its cause, fear of movement, mood, sleep, work status and expectations of recovery
• Drug history - long-term corticosteroids, anticoagulants, immunosuppression, and what analgesia has already been tried

Examination

• Inspection - posture, deformity such as a scoliosis, kyphosis or step in the spinous processes, and any sciatic list
• Palpation - paraspinal muscle tenderness and, importantly, focal bony tenderness over a spinous process, which raises the possibility of fracture, infection or metastasis
• Range of movement - lumbar flexion, extension and lateral flexion; consider the modified Schober test if inflammatory disease is suspected
• Straight leg raise and, where appropriate, femoral stretch test
• Full lower limb neurological examination whenever radicular symptoms are present - tone, power in all major groups, sensation in the L2-S1 dermatomes, knee and ankle reflexes, and plantar responses
• Gait, including heel and toe walking as a rapid screen for L5 and S1 weakness
• Perianal sensation and digital rectal examination if any cauda equina feature is reported
• Targeted general examination - hip movements (groin pain on internal rotation suggests hip rather than spinal pathology), abdominal palpation for an aortic aneurysm or mass, and the peripheral pulses

The STarT Back Tool

The Keele STarT Back Screening Tool is a validated nine-item questionnaire used at the first point of contact in UK primary care to stratify patients by their risk of a poor outcome - that is, of persistent disabling pain rather than of serious pathology. It generates a total score and a psychosocial subscale score, placing the patient into a low, medium or high risk group.^6,7 NICE recommends considering this kind of stratification to match the intensity of treatment to need, so that low-risk patients are not over-treated and high-risk patients are not left to fail conservative care for months.¹

The original randomised trial found that stratified care improved disability outcomes and was cost-effective compared with usual care, largely by directing resource towards the high-risk group.⁶ Subsequent implementation has been more variable in effect, but the tool remains widely used in UK primary care and is worth being able to name and explain.

Differential diagnosis

Not all back pain comes from the back. Non-spinal causes are easily missed if the assessment focuses only on the lumbar spine, and several are immediately dangerous.

• Ruptured or symptomatic abdominal aortic aneurysm - sudden severe back or flank pain with haemodynamic compromise in an older patient, sometimes with a pulsatile mass. This is the non-spinal diagnosis you cannot afford to miss
• Renal colic and pyelonephritis - loin pain radiating to the groin, or loin tenderness with fever and urinary symptoms
• Acute pancreatitis and posterior peptic ulcer - epigastric pain boring through to the back, related to meals or alcohol
• Gynaecological pathology - endometriosis, pelvic inflammatory disease, ovarian pathology, and pregnancy-related pelvic girdle pain
• Hip osteoarthritis - groin pain referred to the buttock and thigh, with pain and restriction on passive internal rotation of the hip
• Polymyalgia rheumatica - proximal shoulder and hip girdle pain and stiffness in someone over 50 with a raised ESR/CRP
• Herpes zoster - unilateral dermatomal burning pain that precedes the rash by a few days
• Fibromyalgia and chronic widespread pain - back pain as part of a wider pattern of widespread tenderness, fatigue and unrefreshing sleep

Investigations

NICE recommends against routine imaging for low back pain in a non-specialist setting, and advises explaining to patients why a scan is not needed.¹ This is one of the guideline's most heavily examined points, and the reasoning matters as much as the recommendation.

When imaging is indicated

• Any red flag raising suspicion of specific pathology - cauda equina syndrome (emergency whole-spine MRI), suspected malignancy, infection or fracture
• Progressive or severe neurological deficit
• Persistent radicular symptoms where an epidural injection or surgical decompression is being considered - imaging must be timed to the decision, not to the complaint
• Suspected lumbar spinal stenosis where decompression is being considered
• Suspected axial spondyloarthritis - X-ray of the sacroiliac joints first, with MRI if the X-ray is normal but suspicion persists⁸

MRI is the imaging modality of choice for the spine: it shows the discs, nerve roots, cord and cauda equina, bone marrow oedema of infection or occult fracture, and epidural collections, all without ionising radiation. Plain X-rays are of limited value in non-specific back pain but remain a reasonable first test for suspected vertebral fracture, though a normal film does not exclude one. CT is used where MRI is contraindicated or where bony anatomy needs detailed definition, such as before surgery.

Blood tests

Bloods are not part of the routine assessment of non-specific back pain. They are directed by suspicion of specific pathology.

• FBC, CRP and ESR - inflammatory or infective pathology; a normal CRP does not exclude indolent discitis but a markedly raised one is informative
• Blood cultures - before antibiotics in suspected spinal infection
• Bone profile including calcium and alkaline phosphatase - hypercalcaemia and a raised ALP in metastatic bone disease
• Myeloma screen - serum protein electrophoresis and serum free light chains, with urinary Bence Jones protein, in an older patient with unexplained bone pain, anaemia, renal impairment or hypercalcaemia
• PSA in men where prostatic metastases are a consideration
• HLA-B27 - only as part of the axial spondyloarthritis pathway, never as a standalone screening test

Management

For non-specific low back pain and for sciatica without red flags, management is conservative, and its central message is activity rather than rest. NICE NG59 is unusually explicit about what not to do, and those negative recommendations are exactly what tends to be examined.¹

Advice and self-management

Every patient should receive clear information about their condition and its favourable natural history, together with encouragement to stay active and continue normal activities, including work, as far as the pain allows. This explicitly replaced the older advice to rest: bed rest delays recovery, causes deconditioning and increases the risk of chronicity, and should be advised against.

• Explain that the pain is common, that serious pathology has been excluded, and that most episodes settle substantially within weeks
• Encourage continuing normal activity and returning to work early, with modified duties if needed, rather than waiting to be pain-free
• Advise against bed rest; brief rest during the most acute phase is acceptable but should not be prolonged
• Promote general exercise, weight management and smoking cessation
• Give clear safety-netting on the cauda equina symptoms that require immediate reassessment, and document that this was done
• Arrange review if symptoms are not improving as expected, or if new features develop

Pharmacological management

Oral NSAIDs are first-line, at the lowest effective dose for the shortest period possible, taking account of gastrointestinal, cardiovascular, renal and hepatic risk, and with a proton pump inhibitor co-prescribed where appropriate - which in practice covers most older patients and anyone with additional risk factors.^1,9 Where an NSAID is contraindicated, not tolerated or ineffective, a weak opioid such as codeine, with or without paracetamol, may be considered for acute pain only and for the shortest possible time.

The rejection of gabapentinoids for sciatica is a genuine change of practice that many clinicians still get wrong, and reflects both the negative trial evidence and the MHRA reclassification of pregabalin and gabapentin as class C controlled drugs. Where pain persists beyond an identifiable nociceptive cause, NICE NG193 on chronic pain becomes the relevant guideline, which similarly advises against starting opioids, NSAIDs, paracetamol or benzodiazepines for chronic primary pain and favours exercise, psychological therapy and, in selected cases, acupuncture or an antidepressant.¹⁰

Non-pharmacological management

A group exercise programme is the core intervention for people with persistent or recurrent low back pain and sciatica - biomechanical, aerobic, mind-body approaches such as yoga or Pilates, or a combination, delivered within the NHS and tailored to the individual's needs and preferences. No single type of exercise has been shown to be clearly superior, which means the best programme is the one the patient will actually do.

• Group exercise programme - the first-line non-pharmacological treatment
• Manual therapy (spinal manipulation, mobilisation or soft tissue techniques such as massage) - only as part of a treatment package that includes exercise, with or without psychological therapy. It is explicitly not recommended in isolation
• Psychological therapy using a cognitive behavioural approach - again, only alongside exercise rather than on its own
• A combined physical and psychological programme - for patients with significant psychosocial obstacles to recovery, or when previous treatment has failed
• Return-to-work support, including liaison with occupational health and phased return where relevant
• Radiofrequency denervation - considered in secondary care for chronic pain thought to arise from the facet joints, after a positive response to a diagnostic medial branch block

Underlying all of this is the biopsychosocial model: persistent back pain is shaped by physical findings, by beliefs and emotional responses, and by social and occupational context, and treating only the first of these produces poor results. Fear-avoidance is the clearest example - a patient who believes movement is causing damage avoids activity, becomes deconditioned and more painful, which reinforces the belief and closes the loop. Breaking that cycle with explanation, graded activity and, where needed, psychological input is often more effective than any analgesic.

Sciatica-specific management

Most sciatica settles with the same conservative approach - staying active, NSAIDs and exercise-based physiotherapy - and time. Where it does not, two further options exist.

• Epidural corticosteroid injection (with local anaesthetic) - may be considered for acute and severe sciatica. It offers short-term relief of leg pain and can be useful as a bridge, but does not improve long-term function and is not recommended for chronic sciatica or for central spinal stenosis causing neurogenic claudication
• Spinal decompression surgery - most often microdiscectomy, considered when non-surgical treatment has not improved pain or function and the imaging findings correspond to the clinical symptoms and level. Surgery produces faster relief of leg pain than conservative care, though the difference in outcomes narrows over one to two years

NICE makes the specific point that a person's BMI, smoking status or psychological distress should not be used to exclude them from referral for a surgical opinion for sciatica.¹ Conversely, disc replacement and spinal fusion are not recommended for non-specific low back pain outside a randomised trial.

When to refer

• Immediately (same day) - suspected cauda equina syndrome, or a rapidly progressive neurological deficit
• Urgently - suspected spinal infection, spinal malignancy or metastatic cord compression, or a vertebral fracture
• For a surgical opinion - sciatica that remains disabling despite an adequate trial of conservative management, typically with radicular symptoms persisting beyond around 4-6 weeks and radiology that matches the clinical level
• For a surgical opinion - lumbar spinal stenosis with neurogenic claudication limiting walking distance despite conservative treatment, where decompression may be considered
• To rheumatology - suspected axial spondyloarthritis, using the NG65 referral criteria (back pain starting before age 45 and lasting more than 3 months, plus additional inflammatory features; HLA-B27 testing may be used to decide borderline cases)⁸
• To a pain service or combined programme - persistent disabling pain with high psychosocial risk despite primary care management

Complications

The dominant complication of low back pain is not structural damage but chronicity and disability. A minority of patients transition from an acute episode to persistent pain, and this small group accounts for the overwhelming majority of the healthcare cost, work absence and long-term disability attributed to back pain. Predicting who they will be is precisely what risk stratification tools attempt to do.

• Chronic pain and physical deconditioning - loss of fitness, strength and mobility as activity is avoided
• Psychological consequences - anxiety, depression, sleep disturbance and catastrophising, which both result from and perpetuate the pain
• Fear-avoidance and disability - the self-reinforcing cycle of avoided movement, deconditioning and worsening function
• Occupational and social impact - sickness absence, job loss, financial strain and reduced independence
• Iatrogenic harm - opioid dependence, NSAID-related gastrointestinal bleeding and renal impairment, and the harms of unnecessary investigation and surgery
• Missed serious pathology - the consequence of not screening for red flags, with delayed diagnosis of cauda equina syndrome, spinal infection or malignancy causing permanent and avoidable harm

Prognosis

The natural history of acute non-specific low back pain is favourable. Most episodes improve substantially within a few weeks regardless of the specific treatment given, with the steepest improvement in the first month, and the majority of people return to normal activity and work. This is the single most useful thing to tell a patient at the first consultation, and it is itself therapeutic.

Recurrence is common, however - a large proportion of patients have a further episode within a year - and a proportion are left with ongoing low-grade or fluctuating symptoms. Framing back pain as a recurrent condition to be self-managed, rather than a one-off injury to be cured, sets more realistic expectations and reduces the distress that accompanies each recurrence.

Sciatica also has a good prognosis with conservative management, though recovery is slower than for non-specific back pain: the majority improve over weeks to a few months, and around half of patients have substantially improved by six weeks. Persistent leg pain beyond that point is the trigger to reconsider imaging and referral. Outcomes are worse where symptoms are severe at onset, where there is a large disc herniation with objective neurological deficit, and - importantly - where psychosocial risk factors are high, which is why these are assessed from the outset rather than after conservative treatment has failed.^2,3

Red flags