Sciatica (Lumbar Radiculopathy)

How sciatica develops

The sciatic nerve is the largest nerve in the body. It forms in the pelvis from the L4, L5, S1, S2 and S3 nerve roots and runs through the buttock and down the back of the thigh, splitting above the knee into branches that supply the lower leg and foot.

In most cases, the problem is not the sciatic nerve itself but one of its nerve roots where it leaves the spine. When a disc herniates, the soft center pushes through the outer ring and presses on the root. Chemicals released from the disc also inflame it, which is why sciatica can be painful even when compression looks small on a scan. Over time, the herniated material often shrinks as the body reabsorbs it, which is why most cases improve.

For symptom-focused advice on what sciatica feels like and home relief, see sciatic nerve pain.

Symptoms by nerve root

L5 and S1 radiculopathy account for most sciatica.

Causes and risk factors

Causes

• Herniated disc at L4-L5 or L5-S1
• Spinal stenosis: narrowing from thickened ligaments, bone spurs and disc bulging, mainly after 60. It causes neurogenic claudication: leg pain and heaviness with walking or standing, eased by sitting or leaning forward
• Spondylolisthesis: slippage of one vertebra on another
• Foraminal narrowing from degenerative disc disease
• Less common: synovial cysts, epidural abscess, tumors, pregnancy-related compression, piriformis muscle compression of the sciatic nerve in the buttock

Risk factors

• age 30 to 50 (disc herniation)
• heavy lifting, twisting, prolonged sitting and vibration (such as long-distance driving)
• smoking, which accelerates disc degeneration
• obesity
• tall height
• previous episodes

Diagnosis

Clinical examination

Diagnosis is mainly clinical. A doctor will:

• map where pain and numbness spread
• test strength in hip, knee, ankle and toe muscles
• check knee and ankle reflexes and sensation
• perform the straight leg raise: reproduction of leg pain below the knee when the straight leg is lifted to 30 to 70 degrees suggests nerve root tension. Pain when the opposite leg is raised (crossed straight leg raise) is highly specific for a disc herniation
• ask about red flags such as bladder symptoms, fever, cancer and weight loss

Imaging and tests

• MRI is the best test, but is not needed in the first 6 weeks unless there are red flags or significant weakness. Disc bulges are common on MRI in people without pain, so findings must match symptoms.
• CT or CT myelogram if MRI is not possible.
• X-rays show spondylolisthesis and arthritis but not discs or nerves.
• Nerve conduction and EMG help when the diagnosis is unclear or to distinguish from peripheral neuropathy.

Treatment

First-line: conservative care

• Stay active: continue normal activity as much as possible; avoid bed rest.
• NSAIDs for short periods if safe. Evidence for many other medicines is weak: gabapentin and pregabalin have not shown clear benefit for sciatica in trials, and opioids are not recommended for long-term use. Oral steroids give at most modest, short-term benefit.
• Physical therapy: exercises tailored to the cause, directional preference exercises, core and hip strengthening, nerve mobilization, and advice on activity.
• Manual therapy combined with exercise may help some people.

Epidural steroid injection

An injection of steroid and local anesthetic around the irritated nerve root, guided by X-ray. It can reduce leg pain for weeks to a few months, helping people stay active while the disc settles. It does not change long-term outcomes or prevent surgery in most people.

Surgery

• Microdiscectomy: removing the part of the disc pressing on the nerve. It relieves leg pain faster than continued conservative care, but outcomes at 1 to 2 years are similar for many people. It is considered for severe pain lasting 6 to 12 weeks despite treatment, progressive weakness, or cauda equina syndrome (emergency).
• Laminectomy (decompression): for spinal stenosis.
• Fusion: in some cases of spondylolisthesis with instability.

Complications

• persistent or chronic pain (in a minority)
• permanent numbness or weakness, including foot drop
• cauda equina syndrome, from a large central disc herniation, which can cause permanent bladder, bowel and sexual dysfunction if not treated urgently

Outlook

Most people recover. About 75% improve substantially within 3 months. Recurrence affects a meaningful minority within a few years. Staying active, strengthening the trunk and hips, managing weight and not smoking reduce the chances of further episodes.

Prevention

• Lift with your legs, keeping loads close to your body, and avoid twisting while lifting.
• Break up long periods of sitting.
• Keep fit with regular exercise that strengthens the core and hips.
• Stop smoking.

Frequently asked questions

What causes sciatica?

About 90% of sciatica is caused by a herniated disc pressing on and inflaming a nerve root in the lower spine. Spinal stenosis is a common cause in older adults. Less common causes include a slipped vertebra (spondylolisthesis), cysts, infection and tumors.

Do I need an MRI for sciatica?

Usually not at first. Most sciatica improves within 6 weeks, and MRI findings do not change early treatment. An MRI is recommended for red-flag symptoms, significant or worsening weakness, or persistent pain when injection or surgery is being considered.

When is surgery needed for sciatica?

Emergency surgery is needed for cauda equina syndrome. Otherwise, surgery is considered for severe, disabling leg pain lasting 6 to 12 weeks despite good conservative treatment, or for progressive weakness. Microdiscectomy relieves leg pain faster, but many people recover without it.

What is the difference between sciatica and lumbar radiculopathy?

They are essentially the same. Lumbar radiculopathy is the medical term for symptoms caused by a compressed or irritated lumbar nerve root. Sciatica describes the resulting pain down the leg along the sciatic nerve. Radiculopathy also includes numbness, weakness and reflex changes.

Can sciatica come back?

Yes. Recurrences are common, especially in the first year or two. Staying active, regular core and hip strengthening, good lifting technique, maintaining a healthy weight and not smoking lower the risk.