What Is Sciatica? Causes, Symptoms, and Treatment

What Is Sciatica?

Sciatica is not a diagnosis — it is a symptom descriptor. It refers to pain that radiates along the course of the sciatic nerve, from the lower back through the buttock and into the posterior or lateral leg, sometimes extending to the foot. The sciatic nerve is the largest and longest peripheral nerve in the body, formed by the L4, L5, S1, S2, and S3 nerve roots converging in the pelvis and travelling through the gluteal region down the posterior thigh before dividing above the popliteal fossa into the tibial and common peroneal nerves. When any portion of this nerve or its contributing nerve roots is compressed, stretched, or chemically irritated, the characteristic radiating leg pain, altered sensation, and potential weakness of sciatica is produced. Understanding the source of sciatic nerve irritation — which varies considerably between individuals — determines the appropriate treatment.

What Causes Sciatica?

The most common cause of true sciatica is lumbar disc herniation — protrusion of the nucleus pulposus through the annulus fibrosus, compressing a nerve root in the lateral recess or intervertebral foramen. L4–L5 and L5–S1 are the most commonly affected levels, producing symptoms in the L5 and S1 dermatomal distributions respectively. Lumbar spinal stenosis — narrowing of the spinal canal or foramina by osteophytes, ligamentum flavum hypertrophy, or facet joint enlargement — produces sciatica-like symptoms, typically bilateral and aggravated by lumbar extension and walking (neurogenic claudication). Piriformis syndrome — compression of the sciatic nerve by the piriformis muscle in the deep gluteal space — produces clinically indistinguishable leg symptoms without spinal pathology. Less common causes include spondylolisthesis, tumour, and direct gluteal trauma. Identifying the specific source through clinical assessment directs management.

Recognising Sciatica

The cardinal feature of sciatica is leg pain that predominates over back pain — pain that travels below the knee is particularly indicative of genuine nerve root involvement. The character is often described as burning, shooting, electric, or deep aching, distinct from the dull muscular ache of referred somatic pain. Neurological features — sensory changes (numbness, tingling, altered sensation) in a dermatomal distribution, weakness in the myotome, or reduced reflexes — confirm nerve involvement rather than simple referred pain. The straight leg raise test (SLR) — which stretches the L4–S1 nerve roots and reproduces sciatic symptoms when positive, typically between 30–70 degrees of hip flexion — is the most sensitive provocative test for lumbar disc herniation with radiculopathy and is used universally in clinical assessment.

Red Flags: When to Act Urgently

Most sciatica is a benign, self-limiting condition that responds to conservative management. However, certain features demand urgent medical assessment. Cauda equina syndrome — compression of the cauda equina nerve roots at the lower lumbar spine — is a medical emergency presenting with bilateral leg pain and weakness, saddle anaesthesia (numbness in the perineal region), and bladder or bowel dysfunction (urinary retention, incontinence, or loss of anal tone). Any combination of these features requires emergency presentation to hospital for imaging and potential urgent surgical decompression. Progressive neurological deficit — worsening weakness in the leg over days to weeks — also warrants urgent imaging and specialist review regardless of pain severity.

Evidence-Based Treatment

The majority of acute sciatica from disc herniation — approximately 80–90% of cases — resolves within six to twelve weeks without surgery. Conservative management is the appropriate first-line approach: relative activity modification (avoiding sustained positions that increase nerve root tension) rather than strict bed rest, which worsens outcomes; manual therapy targeting lumbar mobility, nerve root mobilisation, and reducing adjacent muscular guarding; neural mobilisation exercises (sciatic nerve sliders and tensioners) that improve neural excursion and reduce adhesion around the nerve; specific exercise prescription (McKenzie directional preference assessment identifies centralising movements that reduce disc pressure on the nerve root in many presentations); and education — understanding that imaging abnormalities do not determine prognosis and that movement promotes, rather than impairs, recovery.

When Is Surgery Needed?

Surgical discectomy is indicated when: conservative management has failed to produce meaningful improvement after six to twelve weeks; progressive neurological deficit is present; or cauda equina syndrome requires emergency decompression. When indicated, discectomy produces faster resolution of leg pain and neurological symptoms than conservative management — but six- and twelve-month outcomes are similar for appropriate surgical and non-surgical candidates, as the natural history favours resolution in both groups. Surgery removes the structural compression; it does not change the underlying disc degeneration, movement patterns, and loading behaviours that contributed to the herniation. A comprehensive rehabilitation programme following surgery is essential for reducing recurrence risk.