Ordinary back pain stays in the back. Sciatica does not. It begins in the lower spine or buttock and then travels, often in a sharp, electric line down the back of the thigh, past the knee, and sometimes all the way into the foot. People describe it as burning, shooting, or like an electric shock, and many find it harder to live with than the back pain that comes with it. That travelling quality is the clearest sign that a nerve, rather than a muscle, is the source of the problem.
One useful way to understand sciatica is to follow the nerve itself from the spine to the toes. Problems at different points along that route produce different symptoms, and knowing the route explains why the condition behaves the way it does, why it affects only one leg in most cases, and why treatment depends so much on where the trouble begins.
The Longest Nerve in the Body
The sciatic nerve is the largest and longest nerve in the human body. It is formed from several nerve roots that leave the lower spine, between roughly the fourth lumbar vertebra and the third sacral segment, and join together deep in the pelvis. At its start it is about as thick as a thumb. It passes through the buttock, runs down the back of the thigh, and divides above the knee into branches that supply the muscles and skin of the lower leg and foot.
Because it carries both sensation and movement signals for so much of the leg, irritation anywhere along its length can produce pain, tingling, numbness, or weakness well away from the actual site of the problem. This is also why "sciatica" is best understood as a symptom rather than a diagnosis. It describes pain caused by irritation or compression of the sciatic nerve or its roots, and the real question is always what is irritating the nerve.
Stop One: The Spine
In the large majority of cases, the trouble starts where the nerve roots leave the spinal canal. The most common cause is a herniated or bulging disc. The discs between the vertebrae have a tough outer wall and a softer, gel-like centre. When the wall weakens or tears, the centre can push outward and press on a nearby nerve root, causing both inflammation and mechanical compression. This is most common in people between their thirties and fifties, and often follows a period of heavy lifting, repeated bending, or simply long hours of sitting.
In older adults, a different mechanism is more common. Spinal stenosis is a narrowing of the canal or of the openings through which the nerve roots pass, usually caused by thickened ligaments, bony overgrowth from arthritis, and age-related disc changes. It tends to produce leg pain, heaviness, or tingling when standing or walking, which eases when sitting or leaning forward. Spondylolisthesis, in which one vertebra slips forward over the one below it, can narrow the space for the nerve in a similar way. Less often, bone spurs, spinal injuries, or tumours are responsible.
Stop Two: The Buttock
Occasionally the nerve is compressed not in the spine but as it passes through the deep muscles of the buttock. The piriformis, a small muscle that sits close to the nerve, is sometimes implicated, and the resulting picture is often called piriformis syndrome. Pain here tends to be centred in the buttock, worsens with prolonged sitting or with activities that engage the hip rotators, and may travel down the thigh. This explanation is less common than a spinal cause and is still debated among specialists, which is one reason a careful examination matters. A diagnosis of buttock-level compression should only be reached after a spinal cause has been properly considered.
Stop Three: The Thigh and Leg
This is where sciatica announces itself most clearly. The pain typically runs from the buttock down the back or outer side of the thigh and calf, usually on one side only. It may be accompanied by pins and needles, numbness, or a sensation of heat or cold, and it often worsens with coughing, sneezing, or straining, because these actions briefly raise pressure inside the spinal canal. Sitting for long periods commonly makes it worse, while walking or changing position can bring relief.
The exact path of the symptoms gives doctors a clue to which nerve root is affected. Pain and tingling that run down the outer leg and onto the top of the foot, sometimes toward the big toe, often implicate the fifth lumbar root. Symptoms that run down the back of the calf and into the sole or outer edge of the foot more often implicate the first sacral root. This mapping, combined with testing of strength and reflexes, helps an orthopedist locate the problem without needing to rely on imaging alone.
Stop Four: The Foot
Weakness is a more important sign than pain. If the nerve is compressed enough to interfere with movement, patients may notice difficulty lifting the front of the foot or the big toe, a tendency to trip on kerbs, or a foot that slaps down when walking, a pattern known as foot drop. Difficulty rising onto the toes can point to the other root. Progressive weakness of this kind suggests significant nerve compression and should be assessed promptly rather than watched for weeks.
Is It Really Sciatica?
Not every pain that travels down the leg is sciatica, and distinguishing it from lookalikes is a central part of an orthopedic assessment. Arthritis of the hip commonly causes pain felt in the groin or front of the thigh and is often mistaken for a back problem. Dysfunction of the sacroiliac joint produces pain over the buttock and back of the pelvis that may refer into the thigh but rarely travels below the knee. Muscle strains and trigger points in the buttock can radiate pain in a way that imitates nerve pain. Circulation problems in the leg, such as peripheral artery disease, cause cramping pain with walking that settles with rest, and can resemble the leg symptoms of stenosis. Peripheral neuropathy from diabetes or other conditions typically affects both feet symmetrically rather than one leg.
The difference matters because each of these has a different treatment. Treating a hip problem as a back problem, or the reverse, wastes time and often prolongs suffering.
How Sciatica Is Diagnosed
Diagnosis rests mainly on the history and examination. The clinician asks about the pattern and path of the pain, what makes it better or worse, and whether there is numbness, weakness, or any change in bladder or bowel function. The examination checks strength, sensation, and reflexes in the legs, along with tests that gently tension the nerve, such as the straight leg raise, which reproduces the pain when a compressed nerve root is stretched.
Imaging is not always required. Most sciatica improves with time and conservative care, and scans taken early often show disc changes that are common in people without pain. An MRI is generally reserved for patients with severe or progressive symptoms, signs of significant weakness, red-flag features, or pain that has not responded to several weeks of treatment, particularly when an injection or surgery is being considered. Nerve conduction studies are occasionally used when the diagnosis is unclear.
What Treatment Looks Like
The reassuring news is that most sciatica gets better without surgery. A large proportion of patients improve substantially within six to twelve weeks, and many much sooner, as the inflammation around the nerve settles and, in the case of a disc herniation, the protruding material often shrinks over time.
Initial treatment focuses on staying as active as the pain allows. Prolonged bed rest is no longer recommended, since movement helps recovery and prevents stiffness. Physiotherapy is central, using specific exercises and nerve-mobilising techniques, along with strengthening of the core and hip muscles, to relieve pressure and reduce the chance of recurrence. Medication can help the patient stay mobile during the painful phase. Anti-inflammatory tablets are used short term where appropriate, and medicines aimed at nerve pain may be prescribed when symptoms are severe, though they work for some people and not others and should be taken under medical guidance.
When pain remains severe despite these measures, an epidural steroid injection delivers anti-inflammatory medication close to the irritated nerve root and can provide meaningful relief that allows rehabilitation to progress. Surgery, most often a microdiscectomy to remove the part of a disc pressing on the nerve, is considered when significant pain persists beyond roughly six to twelve weeks of proper conservative care, or sooner when there is progressive weakness or other serious nerve involvement. Surgical outcomes for carefully selected patients are generally good, but the decision depends on the cause, the severity, and the individual's circumstances.
When Sciatica Becomes an Emergency
A small number of cases involve compression of the nerves at the base of the spinal canal, known as cauda equina syndrome. Warning signs include numbness around the groin, genitals, or inner thighs; new difficulty starting or controlling urination; loss of bowel control; and weakness or numbness affecting both legs. This requires emergency assessment and, often, urgent surgery, because delay can lead to permanent damage. Severe, rapidly worsening weakness in a leg, or sciatica accompanied by fever, unexplained weight loss, or a history of cancer, also warrants prompt attention.
Living With It and Preventing a Return
Sciatica can recur, particularly if the underlying causes are never addressed. Regular activity, especially walking and exercises that strengthen the trunk and hips, helps keep the spine resilient. Breaking up long periods of sitting, using a supportive chair, lifting with the legs rather than the back, and maintaining a healthy weight all reduce strain on the lumbar discs. Smoking is associated with poorer disc health and slower recovery, so avoiding it supports the spine as well as the rest of the body.
The Bottom Line
Sciatica is the body's way of reporting that a nerve is irritated, and its distinctive travelling pain is a clue worth taking seriously. Most cases improve with time and conservative treatment, but identifying the underlying cause early allows the right treatment to begin sooner and helps avoid the cycle of repeated flare-ups. Persistent leg pain, numbness, or tingling, and especially any weakness or change in bladder or bowel control, should be evaluated rather than endured.
Pain Travelling Down Your Leg? Find Out Why
If back pain is spreading into your leg, or you are noticing numbness, tingling, or weakness, an accurate diagnosis can identify what is irritating the nerve and guide the right treatment. Our orthopedists examine your spine and symptoms, explain the cause, and recommend a plan suited to your diagnosis.
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