What is Piriformis Syndrome?
Piriformis syndrome is a neuromuscular condition where the piriformis muscle in the deep gluteal space compresses or irritates the sciatic nerve, causing buttock pain that radiates down the leg, mimicking sciatica. 1, 2, 3
Pathophysiology and Anatomical Basis
The piriformis muscle lies deep in the buttock region and has an intimate anatomical relationship with the sciatic nerve, which typically passes beneath the muscle (though in ~16% of individuals, the nerve may pierce through the muscle itself). 2, 4
Compression occurs when excessive muscle tension, spasm, or anatomical variations cause the piriformis to compress the sciatic nerve in the deep gluteal space. 5, 3
The muscle's function varies with hip position: in neutral position it externally rotates the hip, but when the hip is flexed, it internally rotates and abducts the hip—this biomechanical complexity contributes to symptom variability. 2
Clinical Presentation
The hallmark symptom is buttock pain with radiation down the posterior leg along the sciatic nerve distribution. 1, 3, 4
Pain is typically described as dull, aching, sharp, or electrical in character. 1
External tenderness over the greater sciatic notch is a common finding. 4
Symptoms worsen with prolonged sitting, which is a characteristic aggravating factor. 5, 4
Patients may report numbness and paresthesias along the leg, though unlike true lumbar radiculopathy, piriformis syndrome usually does not cause specific dermatomal sensory loss or myotomal weakness. 1, 5
In chronic cases, patients may develop compensatory gait patterns. 1
Common Precipitating Factors
History of severe fall or trauma to the buttocks region. 5
Prolonged sitting (especially on hard surfaces). 5
Athletic activities involving repetitive hip movements. 2
Previous gluteal injections or abscess formation. 5
In many cases, no clear precipitating event is identified. 5
Diagnostic Challenges and Pitfalls
Piriformis syndrome is a diagnosis of exclusion and is often misdiagnosed due to significant symptom overlap with lumbar radiculopathy and other causes of sciatica. 1, 6, 3
The FAIR test (flexion-adduction-internal rotation) has limited clinical utility due to poor specificity, though a negative test may help rule out hip-related pain. 1
Lumbar spine pathology must be excluded in all cases, as radicular pain from L5-S1 disc lesions can closely mimic piriformis syndrome. 1, 7
There are few validated and standardized diagnostic tests, making diagnosis difficult and largely clinical. 6, 4
MRI and EMG are typically performed to exclude other pathology rather than to confirm piriformis syndrome. 5, 4
Ultrasound may show piriformis muscle thickening, but this finding requires further validation. 4
Incidental imaging findings are common in asymptomatic individuals, so clinical correlation is mandatory. 8, 7
Epidemiology
Estimated prevalence is 5-6% of all cases presenting with low back, buttock, and leg pain. 4
May account for up to 17% of patients with chronic low back pain. 4
The anatomical variant where the sciatic nerve pierces the piriformis muscle occurs in ~16% of healthy individuals but is not more common in those with the syndrome, suggesting this anatomical finding alone does not cause the condition. 4
Treatment Approach
Conservative management is the mainstay of initial treatment, focusing on stretching, strengthening, and physical therapy modalities. 2, 6, 3
Treatment protocols should emphasize exercises promoting piriformis flexibility, hip strength, and functional activities to restore pain-free movement. 2
For cases unresponsive to conservative therapy, injections into the piriformis muscle using local anesthetic and corticosteroids can be performed. 5, 6
CT-guided piriformis injection is a safe and effective method, with studies showing full and sustained recovery in the majority of patients. 5
Botulinum toxin (BTX) injections have gained popularity for refractory cases, with some studies demonstrating superior efficacy to corticosteroid injection by relieving sciatic nerve compression and reducing muscle pain from a tight piriformis. 6, 3
Surgical intervention is reserved for cases with variable success rates when all conservative and injection therapies have failed. 4
Key Clinical Caveat
The diagnosis remains controversial in the medical literature, with many cases appearing to represent myofascial pain conditions rather than true focal neuropathy from nerve compression. 4 This underscores the importance of comprehensive evaluation and the need for future research to refine diagnostic criteria and validate treatment approaches. 3