Sciatica: why it hurts, how it is diagnosed and what treatments exist today

The sciatic nerve is the longest and thickest nerve in the human body. It forms from several nerve roots that exit the lower lumbar spine and the pelvis, then runs down the back of the leg to the foot. When that nerve (or, more precisely, one of the roots it arises from) becomes irritated or compressed, the result is sciatica: that characteristic pain that starts in the lower back or buttock and travels down the leg.

In my daily practice, I find that a good share of the patients who arrive labeled with "sciatica" don't actually have true sciatica: they have sacroiliac joint pain, piriformis syndrome, or referred low back pain that doesn't involve the nerve root. The distinction matters, because each condition has a different treatment — and treating them all as if they were herniated discs is one of the reasons so many cases of sciatica become chronic.

What few patients realize is that sciatica is not a disease in itself, but a symptom. And the same "sciatica-type" pain can have very different causes, each with its own treatment.

The most common causes

Lumbar herniated disc

This is the best-known cause. The intervertebral disc herniates and compresses a nerve root, usually at L4-L5 or L5-S1. It is typical in young to middle-aged adults and generally carries a good prognosis with conservative treatment.

One nuance I repeat often in the office: not every herniation seen on an MRI explains the pain. Studies have found disc herniations and bulges in close to 40% of people over 40 who have never had back pain. So when a patient comes in with an MRI and a diagnosis of "sciatica caused by a herniated disc," the first step is to check whether their pain actually matches the nerve root affected by that herniation. When the two don't line up, the problem usually lies somewhere else.

Lateral recess or foraminal stenosis

With aging, the spaces where the nerve roots exit narrow due to osteoarthritis, ligament thickening or facet hypertrophy. This is the most common cause of sciatica in people over 60. The pain typically worsens with walking or standing and eases with sitting or leaning forward.

Piriformis syndrome

The piriformis is a deep muscle in the buttock. When it goes into spasm or becomes inflamed, it can compress the sciatic nerve as the nerve passes by. It causes buttock pain that radiates down the leg and usually worsens after long periods of sitting or when crossing the legs. It is often mistaken for a herniated disc, yet its treatment is completely different.

Sacroiliitis

When the sacroiliac joint becomes inflamed or degenerates, it produces pain that can mimic sciatica. It is typically located in the buttock but can radiate to the back of the thigh. The diagnosis is confirmed with a diagnostic block of the joint.

To my mind, this is one of the most underestimated diagnoses in patients who arrive labeled as "sciatica that isn't responding." When a patient describes the pain as "right here," pointing with one finger exactly at the lumbar dimple, and it worsens when going from sitting to standing or when climbing stairs, the sacroiliac joint is the first place I look. An image-guided diagnostic block is what ultimately confirms it — and it is often the first step of treatment as well.

Other, less common causes

Tumors, infections, traumatic injuries to the sciatic nerve in the gluteal region (from injections or trauma), and in some cases gynecological or pelvic conditions. These are less common, but they need to be considered when the clinical picture doesn't fit what you would expect.

How it is diagnosed

Diagnosing sciatica combines several tools:

A detailed medical history

This is the most important part. How the pain started, what makes it worse, what relieves it, whether there is weakness, numbness or tingling, past medical history, previous treatments. A thorough history alone points toward the likely cause.

Physical examination

Specific maneuvers such as the straight leg raise (Lasègue) test, the Bonnet test, and a neurological exam of reflexes, strength and sensation. A well-performed physical exam provides more information than many imaging studies.

Imaging

Lumbar MRI is the study of choice for evaluating herniated discs, stenosis or degenerative changes. Plain X-rays add little in sciatica except in a few specific situations. Electromyography can help in selected cases where there is muscle weakness and the affected root needs to be pinpointed.

My rule before ordering an MRI is to wait 4 to 6 weeks if the symptoms started recently and there are no red flags (progressive weakness, loss of bladder or bowel control, fever, a history of cancer, unexplained weight loss). The reason is twofold: most cases of sciatica improve within that window with appropriate treatment, and the earlier the MRI is done, the more likely it is to turn up "findings" that end up confusing both doctor and patient. If, on the other hand, there is a neurological deficit, a red flag, or the symptoms aren't improving, the MRI is ordered without delay.

Available treatments

Medication

Anti-inflammatories on a structured schedule, medication for neuropathic pain (when there is clear radiating pain with tingling), and muscle relaxants for associated muscle spasm. This is the first step in most cases.

Targeted physical therapy

Tailored to the cause: for piriformis syndrome, stretching of the posterior chain; for a herniated disc, disc centralization techniques; for stenosis, core strengthening and flexion-based postures. The physical therapist should know the specific condition being treated.

Interventional nerve blocks

• Lumbar epidural injection: for sciatica caused by a herniated disc or stenosis. It delivers corticosteroids and local anesthetic near the inflamed nerve root.
• Selective nerve root block: when the pain is suspected to come from one specific root.
• Piriformis muscle injection: when that particular muscle is the cause.
• Sacroiliac joint block: both diagnostic and therapeutic for sacroiliitis.

Radiofrequency ablation

In selected cases where the pain responds to nerve blocks but the relief is short-lived, radiofrequency ablation offers longer-lasting relief (6-12 months or more).

Surgery

Reserved for cases with progressive neurological deficit, cauda equina syndrome, or disabling pain that has not responded to 8-12 weeks of well-conducted conservative treatment.

What to expect from recovery

Most cases of sciatica, when properly treated, improve significantly within 6 to 12 weeks. Some take longer, especially when there is a significant neuropathic component. Patience with treatment, consistent physical therapy and lifestyle changes (posture, weight, activity) matter just as much as medication or procedures.

The goal of good treatment is not just to relieve the pain of the moment, but to understand what led to that pain in order to reduce relapses.

When a patient comes back at six months without a relapse, it is almost always because they understood where their pain was coming from and what was triggering it. That's why, at every first visit, I spend more time explaining to the patient what is happening to them than talking about procedures. Sciatica that resolves with an injection and returns three months later hasn't been properly treated: it has been silenced, not resolved.

Dr. Mauricio Casarsa

Anesthesiologist, specialist in Pain Medicine and Interventional Pain Management. Postgraduate training at UBA (Fundación Dolor) and UNLP (CAIDBA). Staff physician at Hospital Alemán, Buenos Aires.

MN 137756 · San Isidro · Villa Urquiza