Overview
The sciatic nerve is the largest nerve in the body. It runs from the lower back, through the buttock and down the back of the leg. Sciatica is the set of symptoms that appear when this nerve is pressed on or irritated.
Sciatica is a symptom rather than a disease in itself, so the aim of an assessment is to find what is affecting the nerve. Most people improve over weeks to months, although it can come back.
Symptoms
The pain usually affects one side. It can be sharp, burning or like an electric shock, and it travels down the back of the leg, sometimes as far as the calf, the foot or the toes.
There may also be tingling, numbness or weakness in the leg or foot. The pain is often worse on moving, coughing or sneezing, and after sitting for a long time. Back pain may be present as well, but it is usually milder than the leg pain.
When to see a doctor
See a doctor within the next few days if the pain has not improved after a few weeks of self-care, if it is getting worse, if it stops ordinary activities or sleep, or if there is numbness or weakness in one leg or foot.
Causes
The commonest cause is a slipped disc, where the soft centre of a disc in the spine pushes out and presses on a nerve root as it leaves the spinal canal.
Other causes are narrowing of the spinal canal, a vertebra slipping forward out of line, and injuries such as a fracture of the pelvis. In many people no single cause can be found.
Risk factors
- Older age, as the discs and joints of the spine change
- Work with heavy lifting, repeated bending or twisting
- Long hours of sitting or driving
- Being overweight
- Doing little physical activity
- Smoking
- An earlier episode of back pain or sciatica
Complications
Most sciatica settles without lasting effects. If a nerve stays compressed, numbness or weakness in the leg or foot can persist, and pain that lasts for months can disturb sleep, work and mood.
Squeezing of the whole bundle of nerves at the base of the spine is rare. It can cause lasting loss of bladder and bowel control if it is not treated quickly, which is why those symptoms are treated as an emergency.
Prevention
- Being physically active most days
- Exercises that strengthen the stomach, back and hip muscles
- Keeping to a healthy weight
- Lifting with the knees bent and the load held close to the body
- Breaking up long spells of sitting or driving
- Not smoking
Diagnosis
A doctor asks where the pain travels, how it started and what makes it worse, then examines the back and legs and tests power, sensation and reflexes to work out which nerve is affected.
Most people do not need a scan. An MRI or of the spine is used when symptoms are severe or are not settling, when there is weakness or numbness, or when an injection or surgery is being considered, so the cause and its exact position can be seen.
Treatment
Most sciatica is managed without surgery. Carrying on with normal activities, doing gentle exercises and stretches, and using a heat pack all help. Sitting or lying down for long periods is best avoided.
A pharmacist or doctor can advise on pain relief that suits the person. Physiotherapy adds a programme of exercise with advice on posture and movement, and is often the next step when self-care is not enough.
When pain is severe or is not settling, a specialist may suggest an injection around the nerve, a procedure that uses heat to stop a nerve carrying pain signals, or decompression surgery to take pressure off the nerve. These are for a minority, and the decision rests on the examination and the scan together.
Myths and facts
Things people often say about this. Open each one to see what is true.
Myth“With sciatica you must lie flat and rest until the leg pain has gone.”What is true?
Fact
Long spells of sitting or lying down are not advised for sciatica. Carrying on with normal activities and doing gentle exercises is what health services recommend, building the amount up as the pain allows.
Myth“Sciatica always ends in spine surgery.”What is true?
Fact
Most sciatica settles without an operation, over weeks to months. Exercises, pain relief and physiotherapy are the usual treatment. Injections and decompression surgery are offered to a minority, when the pain is severe or is not settling.
Myth“Pain running down the leg always means a slipped disc.”What is true?
Fact
A slipped disc is the commonest cause, but sciatica can also come from narrowing of the spinal canal, a vertebra slipping out of line, or an injury. In many cases no single cause is found, which is why the examination matters more than the label.
Questions to ask your doctor
Tick the ones you want answered and take them with you.
Common questions
How long does sciatica usually last?
It often eases within weeks, and most people are better within a few months. Some have it for longer, and it can return later. If the pain is not improving after a few weeks, or is getting worse, that is the point to see a doctor rather than to wait.
Is walking good or bad for sciatica?
Gentle walking and regular movement are encouraged, because long spells of sitting or lying down tend to make sciatica worse. Build the distance up slowly and stop if the leg pain sharply increases. If walking brings on new weakness or numbness, see a doctor.
Can sciatica cause permanent damage to the leg?
That is uncommon. Most people recover fully. Numbness or weakness can persist if a nerve stays compressed, which is one reason why weakness that is getting worse should be looked at quickly rather than left.
Will an MRI tell me exactly what to do?
An MRI shows the structure of the spine, but it does not decide the treatment on its own. A doctor reads it alongside the symptoms and the examination. Most people with sciatica improve without a scan, and imaging matters most when severe symptoms persist or an operation is being considered.