“Sciatica” is not a diagnosis. It is a word for a pain that runs from the buttock or lower back into one leg — and for the question of where it comes from. The answer is usually the disc, but not always. This page explains how we tell the different causes apart, what you can do yourself in the first few days, and when you should not wait.
A pain that runs into the leg has several possible sources. Exactly where it runs, what makes it worse and what relieves it almost always tells us which one it is.
What “sciatica” means
The sciatic nerve is the thickest nerve in the body. It is formed from several nerve roots of the lower lumbar spine and the sacrum, runs down beneath the buttock muscles along the back of the thigh and divides behind the knee. If one of its roots is irritated or compressed at the spine, you do not feel it in the back but where the nerve leads: in the buttock, at the back or side of the leg, often as far as the foot. Doctors call this sciatica or, more precisely, radiculopathy — the root is the problem, not the nerve itself.
Not every leg pain is root pain, however. Joints and muscles can also “refer” pain into the leg without any nerve being involved. This pain is duller, less sharply defined and usually does not reach below the knee; the technical term is pseudoradicular. Telling the two apart is the first step of every assessment, because it decides what makes sense — and what does not.
How we tell where it comes from
Three questions contribute most. Exactly where does the pain run, and does it go below the knee? Root pain follows a strip that you can trace with your finger. What makes it worse — coughing and sitting, walking and standing, turning over in bed, climbing stairs? And is there tingling, numbness or weakness, and where? Then the examination: strength of the foot and toes, reflexes, sensation, nerve stretch signs, mobility of the hip and the sacroiliac joint, tenderness in the buttock. In most cases this points clearly in one direction before any image has been taken.
Imaging is therefore not the first step. An MRI scan makes sense if there are warning signs, if there is weakness or paralysis, and if the symptoms have not improved after a few weeks and a treatment decision depends on it. A scan without such a question mainly shows signs of ageing that people without symptoms have too.
The most common causes
Herniated disc
By far the most common cause of true sciatica. Typical: a sharp, pulling pain along a strip down to below the knee, often into the foot or toes, worse when coughing, sneezing, sitting and bending forward, often of sudden onset, frequently in middle adulthood. With it, tingling or numbness in the same strip, sometimes weakness when lifting the foot or standing on tiptoe. The back itself can be remarkably quiet.
Spinal stenosis and foraminal stenosis
The wear-related narrowing of the spinal canal, mostly in older age. Typical: symptoms in one or both legs that come on when walking and standing and go away again when sitting or bending forward; the walking distance gets shorter, cycling is fine. If only the exit opening of one root is narrow, the picture resembles a herniated disc — but it has developed slowly, is worse when standing and better when sitting.
Sacroiliac joint (SI joint)
The joint between the sacrum and the pelvis. Typical: a deep, one-sided pain below the belt line that you can point to with one finger, often radiating into the buttock and the back of the thigh, rarely below the knee. Worse when turning over in bed, standing up from sitting, standing on one leg, often after pregnancies or falls. No tingling, no weakness. Targeted loading tests of the joint point the way; if needed, an anaesthetic injection into the joint under imaging guidance confirms the diagnosis.
Deep buttock muscles (piriformis)
The sciatic nerve passes beneath the piriformis muscle, sometimes right through it. If this muscle is tense or thickened, it can irritate the nerve. Typical: pain deep in the buttock, worse with prolonged sitting, driving and climbing stairs, with tenderness at one particular spot and radiation into the back of the thigh; the spine itself is unremarkable. This cause is much rarer than a herniated disc and is usually identified by excluding the others.
Hip joint
Hip osteoarthritis likes to radiate into the groin and the front of the thigh down to the knee, sometimes into the buttock. Typical: start-up pain after sitting, pain when tying shoes and getting into the car, restricted rotation of the hip on examination. No tingling, no numbness. An X-ray of the hip clarifies more here than an MRI of the spine.
- A strip down to the foot, worse when coughingPoints to the disc.
- Heavy legs when walking, better when sittingPoints to a narrowing of the spinal canal.
- One spot below the belt line, turning in bed hurtsPoints to the sacroiliac joint.
- Deep in the buttock, sitting hurts, back is freePoints to the buttock muscles.
- Groin and front of the thigh, tying shoes is difficultPoints to the hip.
These patterns are rules of thumb, not diagnoses. They help you describe your symptoms — we make the attribution together after the examination. More than one cause at the same time is possible, and in older age even common.
Warning signs
With three signs, sciatica is not a case for the waiting list but for the emergency services: numbness in the area of the buttocks and perineum, a new problem passing water or opening the bowels, a weakness or paralysis that increases within hours or days. You should have the following assessed within a few days: new weakness in the leg or foot, pain with fever, pain after a fall, and pain that does not ease at night. More on the page Warning signs.
What you can do now
- Keep moving. Bed rest delays recovery. Walk as far as you can and break up periods of sitting. Lying on your back with your lower legs raised on a chair or cushion takes the pressure off for the night.
- Painkillers, used purposefully. An anti-inflammatory for a few days at the lowest effective dose, provided nothing speaks against it. Ask at your GP practice or pharmacy what fits with your other medicines.
- Warmth, if it helps. For the buttock and back; with an inflamed nerve it does not always help, but it does no harm.
- Check your foot. Once a day: stand on your heels, stand on tiptoe, lift your big toe. If this gets weaker, get in touch.
- No scan on your own initiative. An MRI without a question answers no question. It shows changes almost everyone has and creates worries that were not there before.
When you should make an appointment
If the pain has not clearly improved after about two weeks, if tingling or numbness are added to it, if it stops you sleeping or working, or if you simply want to know where it comes from. You do not need a referral or an MRI for this. Bring what you have — scans on CD, doctors’ letters, your list of medicines — and come even if none of these is available. What happens at the first appointment is on the page Your first appointment.
How it usually goes on
Sciatica caused by a herniated disc has a favourable course in most cases. In one survey, around 60 out of 100 people affected had mild to moderate symptoms that improved markedly within three months. The irritated nerve needs time; tingling and numbness last longer than the pain. With a narrowing of the spinal canal, symptoms often stay at a level for years that people can live with. Joint and muscle causes usually respond well to targeted treatment. Surgery is not the first step for any of these causes — and for most people it is never needed.
The matching conditions
If you have recognised yourself in one of the patterns, here you will find the detailed pages with course, diagnosis and treatment with and without surgery:
- Herniated disc of the lumbar spine — the most common cause of true sciatica, with what you should know about waiting, injections and surgery.
- Spinal stenosis — the narrowing of the spinal canal with the short walking distance, including the narrowing in the nerve exit opening.
- Warning signs — the few signs with which you should not wait for an appointment.
On the sacroiliac joint, the deep buttock muscles and the hip we advise you in the consultation; if the cause lies in the hip, we refer you on to suitable orthopaedic treatment.