Sciatica: Causes, Diagnosis & Treatment Options

Sciatica is pain that travels from the lower back, through the buttock, and down the leg along the path of the sciatic nerve. It is important to understand that sciatica is a symptom and not a diagnosis in its own right — it describes where the pain is felt, while the cause lies in an irritated or compressed nerve in the lower spine. Reassuringly, most episodes settle with time and non-surgical care.

What is sciatica?

The sciatic nerve is the largest nerve in the body. It is formed from several nerve roots that leave the lower part of the spine, joins together in the pelvis, and runs down the back of each leg. When one of those nerve roots is irritated or compressed where it exits the spine, pain can be felt anywhere along the nerve’s course — often more in the leg than in the back itself.

Because sciatica is a pattern of pain rather than a single condition, the same leg pain can have different underlying causes. Working out which structure is responsible guides the most suitable treatment.

Which parts of the spine are affected?

Sciatica almost always arises from the lumbar spine — the lower back — where the nerve roots that form the sciatic nerve emerge. Problems at these levels can press on a nerve root and refer pain down the leg in a recognisable pattern, sometimes reaching below the knee to the foot.

The precise distribution of pain, numbness, or weakness can suggest which nerve root is involved, which is helpful during examination.

Causes and risk factors

The classic cause of sciatica is a slipped (herniated) disc, where part of a spinal disc bulges and presses on a nearby nerve root. Other causes include:

• Spinal stenosis, a narrowing of the spinal canal or nerve passages, often related to age-related wear
• Degenerative changes in the discs and joints of the lower spine
• A slipped vertebra (spondylolisthesis) narrowing the space for a nerve
• Less commonly, other causes pressing on the nerve

Factors that may increase the likelihood of an episode include increasing age, heavy or repetitive lifting, prolonged sitting, being overweight, and a previous episode of sciatica.

Symptoms and warning signs

The hallmark is pain that radiates from the lower back or buttock down the leg, frequently felt below the knee and sometimes into the foot. It may be accompanied by tingling, pins and needles, or numbness, and is often made worse by sitting, coughing, or sneezing. Leg pain is commonly more troublesome than the back pain itself.

Certain features are red flags and need urgent assessment rather than watchful waiting:

• Numbness around the back passage, genitals, or inner thighs
• Difficulty passing urine, loss of bladder control, or loss of bowel control
• Weakness affecting both legs, or weakness that is significant or getting worse
• Fever, unexplained weight loss, or a history of cancer with new symptoms

These can indicate a serious problem and should be reviewed without delay.

How sciatica is diagnosed

Diagnosis is largely clinical. A history of where the pain travels, together with a physical examination of movement, sensation, reflexes, and power in the legs — including tests that gently stretch the nerve — usually identifies the affected nerve root and the likely cause.

Imaging is not required for everyone. An MRI is the most useful scan when one is needed, as it shows the discs, nerves, and spinal canal in detail. It is generally reserved for symptoms that are severe, that persist despite treatment, or where the result would change management. The scan is always interpreted alongside the clinical picture, because imaging changes are common and do not always explain the pain.

Non-surgical treatment

Most people improve without surgery, and conservative care is the starting point. It usually includes:

• Staying active, with a gradual return to normal activity rather than prolonged bed rest
• Pain relief, using simple analgesia and other medicines as advised to keep moving
• Physiotherapy and a structured exercise programme to restore movement, strength, and confidence
• Activity and posture advice to reduce aggravating loads during recovery

In selected cases that are slow to settle, spinal injections around the affected nerve may be used to reduce inflammation and help with rehabilitation. The emphasis throughout is on supporting the body’s natural recovery.

When surgery is considered

Surgery is considered only for a minority of people. It may be appropriate when leg pain from a clearly identified compressed nerve has not settled after an adequate period of non-surgical care, or when there is significant or progressing weakness. The most common procedure for a herniated disc is microdiscectomy, which relieves pressure on the nerve.

Surgery is also considered urgently in the red-flag situations described above. The decision weighs the cause, the severity and duration of symptoms, and the person’s overall health, and is made together rather than on imaging alone.

Recovery and outlook

The outlook for sciatica is generally good. Many episodes ease over a number of weeks, and most people return to their usual activities. Recovery is not always steady, and some experience flare-ups or further episodes over time. Where surgery is needed for persistent nerve compression, it often relieves leg pain effectively, though timelines vary between individuals. Keeping active and maintaining general fitness supports recovery and may reduce the chance of recurrence.

When to see a spine specialist

It is reasonable to seek assessment if sciatica is severe, is not improving despite several weeks of conservative care, or keeps returning. Urgent review is needed for numbness around the back passage or genitals, difficulty passing or controlling urine, loss of bowel control, or weakness that is significant or worsening — these may signal a serious problem requiring prompt attention.