Piriformis Syndrome vs True Sciatica: Clinical Reasoning
Muscle Action & Synergy · 7 min read · 2025-11-22
Introduction
"Sciatica" is a symptom, not a diagnosis. True sciatica refers to radicular pain caused by compression of the sciatic nerve roots (usually L4–S1) in the lumbar spine. Piriformis syndrome is a peripheral compression of the sciatic nerve by the piriformis muscle in the buttock. The symptoms overlap significantly, but the examination findings are different.
True Sciatica (Lumbar Radiculopathy)
Cause: Disc herniation (most common), foraminal stenosis, or spondylolisthesis compressing a nerve root.
Pain pattern: Radiates from the low back through the buttock and down the posterior thigh, following a dermatomal distribution. L5: lateral leg and dorsal foot. S1: posterior leg and sole.
Key findings:
- Positive straight leg raise (SLR) — reproduces leg pain at <60°
- Neurological deficits — weakness, sensory loss, reflex changes
- Back pain typically accompanies the leg pain
- Symptoms reproduced by lumbar flexion (increasing disc pressure)
- Contralateral (crossed) SLR is highly specific for disc herniation
- Coughing, sneezing, and straining increase symptoms (increased intrathecal pressure)
Piriformis Syndrome
Cause: The sciatic nerve passes deep to (or in some anatomical variants, through) the piriformis muscle. Spasm, hypertrophy, or inflammation of the piriformis can compress the nerve.
Pain pattern: Deep buttock pain radiating down the posterior thigh. May extend below the knee but typically does not follow a strict dermatomal pattern. Sitting on hard surfaces is very uncomfortable.
Key findings:
- Tenderness over the piriformis (deep palpation in the buttock, midway between the sacrum and greater trochanter)
- Positive FAIR test (Flexion, Adduction, Internal Rotation of the hip — reproduces buttock pain)
- Positive seated piriformis stretch test
- Negative straight leg raise (or only positive at >60° with buttock pain, not true radicular pain)
- No neurological deficits (no weakness, no reflex changes)
- No back pain — the symptoms are purely in the buttock and leg
- Prolonged sitting aggravates symptoms (direct compression of the piriformis on the nerve)
The Key Differentiators
Clinical Pearl
The seated piriformis stretch is the most practical office test: patient seated, affected ankle on opposite knee, lean forward. If this reproduces the familiar buttock and leg pain, piriformis syndrome is likely. This test loads the piriformis without involving the lumbar spine.
Summary
Back pain + positive SLR + neurological deficits = lumbar radiculopathy. No back pain + negative SLR + positive FAIR test + deep buttock tenderness = piriformis syndrome. The straight leg raise is the single most important differentiating test.