Sciatica: Causes, Signs, and Treatment

What Is Sciatica?

Sciatica, popularly known as "sciatic pain", refers to pain that radiates along the path of the sciatic nerve — the largest and longest nerve in the human body. This pain typically begins in the lumbar or gluteal region and travels down the posterior aspect of the thigh, possibly reaching the leg and foot.

It is important to differentiate sciatica from low back pain. While low back pain refers to pain localized in the lumbar region, sciatica specifically involves pain radiating to the lower limb, following the path of the sciatic nerve or of its nerve roots (L4, L5, S1, S2, S3).

Sciatica is not a diagnosis in itself but rather a symptom that indicates compression or irritation of the sciatic nerve or its roots. The most common causes include lumbar disc herniation, spinal canal stenosis, and piriformis syndrome.

Epidemiology

Sciatica affects 1% to 5% of the population at any given time, with a lifetime prevalence estimated at 10% to 40% depending on the definition used. It is more common in men and in the 30-to-50 age range.

Risk factors include age (disc degeneration), above-average height, obesity, smoking, work involving heavy lifting, and exposure to vibration (professional drivers). Genetic factors also contribute, shaping the composition and resilience of the intervertebral discs.

Pathophysiology

The sciatic nerve is formed by the union of the L4, L5, S1, S2, and S3 nerve roots. It emerges from the pelvis through the greater sciatic foramen, passes under (or, in 15% of the population, through) the piriformis muscle, and descends along the posterior aspect of the thigh to the popliteal fossa, where it divides into the tibial and common fibular nerves.

Principal Causes

Mechanisms of Radicular Pain

Sciatic pain results from two main mechanisms. Direct mechanical compression of the nerve root causes focal demyelination and blockade of nerve conduction, leading to numbness and weakness. Chemical inflammation from contact of the nucleus pulposus with the nerve root releases mediators such as phospholipase A2, TNF-alpha, and interleukins, which sensitize nociceptors.

Studies show that chemical inflammation is at least as important as mechanical compression — and possibly more so. This explains why herniation size does not correlate directly with pain intensity, and why large herniations can be asymptomatic.

Symptoms

The cardinal symptom of sciatica is pain radiating from the lumbar spine or gluteal region into the lower limb, following a specific dermatomal pattern that depends on the nerve root involved.

Patterns by Nerve Root

Diagnosis

The clinical diagnosis of sciatica is based on the characteristic history and provocative tests on physical examination. The straight leg raise test (Lasegue), positive between 30 and 70 degrees, has approximate sensitivity of 91% (Deville 2000 meta-analysis in surgical populations) with low specificity (~25-30%) — which limits its value as an isolated test and reinforces the need for clinical correlation.

The crossed Lasegue test (raising the contralateral leg reproduces pain on the symptomatic side) is less sensitive but highly specific (88%) for disc herniation, and is considered one of the most valuable tests.

Piriformis Syndrome

Piriformis syndrome occurs when the piriformis muscle — in the deep gluteal region — compresses or irritates the sciatic nerve as it passes through the greater sciatic foramen. In about 15% of the population, the sciatic nerve passes through the muscle itself, making them anatomically more susceptible. The clinical picture includes deep gluteal pain that worsens with prolonged sitting, climbing stairs, and resisted internal hip rotation.

Distinguishing it from sciatica due to disc herniation is essential: in piriformis syndrome, lumbar spine MRI is normal or shows irrelevant changes, the Lasegue sign is often negative, and the pain is predominantly gluteal rather than lumbar. The FAIR test (hip flexion, adduction, and internal rotation) reproduces symptoms with good specificity. Treatment includes piriformis stretching, acupuncture, and, in refractory cases, local injection.

Lumbar Spinal Stenosis

Lumbar spinal canal stenosis is a frequent cause of pseudo-sciatica in older patients. Unlike classic sciatica from disc herniation, stenosis typically causes bilateral neurogenic claudication — pain, heaviness, and weakness in both legs while walking, relieved by sitting or leaning the trunk forward (the "shopping cart" position). Lumbar flexion widens the canal and temporarily relieves compression.

Distinguishing this from peripheral vascular claudication is clinically important: in vascular claudication, relief comes simply from stopping (no need to sit), peripheral pulses may be reduced, and Doppler ultrasound of the lower-limb arteries confirms the diagnosis. Lumbar MRI shows the degree of stenosis and guides surgical planning when necessary.

Sacroiliitis

Inflammation of the sacroiliac joints can cause pain in the gluteal region and posterior thigh that mimics sciatica. Sacroiliitis can be mechanical (joint dysfunction) or inflammatory, the latter often associated with spondyloarthropathies such as ankylosing spondylitis, psoriatic arthritis, or reactive arthritis. The classic pain worsens on rising from a chair, on single-leg weight-bearing, and after periods of immobility.

Positive sacroiliac stress tests — FABER (hip flexion, abduction, and external rotation), FADIR, and the iliac compression test — point to the sacroiliac joint as the source of pain. When spondyloarthropathy is suspected, the workup should include HLA-B27, acute-phase proteins, and sacroiliac MRI, which can show bone edema before any radiological abnormality.

Gluteal Myofascial Pain

Trigger points in the gluteus medius and minimus produce referred pain along the lateral and posterior thigh and leg, easily confused with true sciatica. This myofascial "pseudo-sciatica" is particularly common in patients with antalgic compensatory posture from chronic low back pain, in athletes, and in workers who sit for long periods. The absence of objective neurological deficit (no abnormalities of reflexes, strength, or sensation) is the crucial distinguishing feature.

Diagnosis is confirmed by palpating taut bands in the gluteal muscles that reproduce referred pain in the typical pattern. Dry needling of these trigger points by the medical acupuncturist is the treatment of choice, producing immediate and lasting relief from pseudo-sciatica. Combining this with gluteus medius strengthening and postural correction prevents recurrence.

Spinal Tumor or Hematoma

Although rare, intracanal space-occupying lesions — primary tumors, metastases, or epidural hematomas — can compress the conus medullaris or cauda equina, producing radicular pain that mimics sciatica. The warning features that distinguish these serious conditions from benign sciatica include progressive, unrelenting pain with no relieving position, severe nighttime pain that wakes the patient, unexplained weight loss, personal or family history of cancer, and persistent fever.

Progressive neurological deficit — weakness that worsens over days or weeks, unlike sciatica from herniation, which tends to improve — is the most concerning sign and demands urgent whole-spine MRI. Cauda equina syndrome (loss of sphincter control, saddle anesthesia) is an absolute neurosurgical emergency, with a therapeutic window of hours to avoid permanent sequelae.

Treatments

Conservative treatment is first-line for most cases of sciatica. About 90% of patients improve without surgery. The approach should be multimodal, combining pain control, exercise, and education.

Conservative Treatment

NSAIDs are the first pharmacological option for control of pain and inflammation. For significant neuropathic pain, gabapentin or pregabalin can be added, although their specific efficacy for sciatica is modest according to recent evidence.

Oral corticosteroids in a short course (5-7 days) can be useful in the acute phase to reduce perineural edema. Epidural injections with corticosteroids can provide temporary relief and facilitate adherence to physical therapy.

Physical therapy with directed exercises — including the McKenzie method (lumbar extension), stabilization exercises, and neurogliding (neural mobilization) — demonstrates efficacy in reducing pain and improving function.

Surgical Treatment

Microdiscectomy is the standard procedure for disc herniation with refractory sciatica. It has a success rate of 85-90% in relieving radicular pain. Surgery provides faster relief than conservative treatment, but long-term results (2-4 years) tend to equalize.

The choice between surgery and conservative treatment depends on pain intensity, presence of neurological deficit, functional impact, and patient preference. Except in emergencies (cauda equina syndrome, progressive motor deficit), there is no urgency to operate.

Acupuncture as Treatment

Acupuncture is used as an adjuvant therapy for sciatica, with evidence of efficacy mainly in pain control and functional improvement. Studies suggest that electroacupuncture may be especially effective in this condition.

Proposed mechanisms in sciatica include descending pain modulation in the dorsal horn of the spinal cord, reduced pro-inflammatory cytokines at the site of radicular compression, and improved perineural microcirculation, which facilitates nerve recovery.

Acupuncture can be especially useful while the patient is waiting for the herniation to resolve on its own, helping control pain and improve quality of life without the side effects of prolonged medication.

Prognosis

The prognosis for sciatica is generally favorable. Most episodes improve significantly within 6 to 12 weeks with conservative treatment. Even large disc herniations can reabsorb naturally over months.

Myths and Facts

When to Seek Medical Help

Although sciatica often improves on its own, some signs require urgent medical evaluation to prevent permanent neurological damage.