Diagnosing and Treating Piriformis Syndrome​

Piriformis syndrome, first described in 1928, arises when a hypertonic or irritated piriformis muscle compresses the proximal sciatic nerve. (1) This pressure causes neurologic ischemia, congestion, local inflammation, and radicular complaints. (2) Researchers estimate that piriformis syndrome contributes to up to one-third of all back pain. (3,4)

The piriformis muscle originates on the anterolateral surface of the mid-portion of the sacrum and inserts on the superior medial aspect of the greater trochanter. When the hip is extended, the piriformis functions primarily as an external rotator of the thigh, with secondary contributions toward flexion. The muscle assists in abduction when the hip is flexed to 90 degrees. (3) The sciatic nerve has a variable relationship to the piriformis muscle. In the majority of the population, the sciatic nerve travels deep to the muscle. Approximately one-fourth of the population is anatomically predisposed to piriformis syndrome because their sciatic nerve passes through the muscle, splits the muscle or both. (5,6) The innervation to the piriformis is somewhat variable, but typically consists of 2-3 branches, most commonly the superior gluteal nerve (70%) and the ventral rami of S1 (85%) and S2 (70%). (32)

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Like many other lower extremity biomechanical problems, the presence of a Morton foot (longer second digit) is thought to be a predisposing factor. (7) The condition is most prevalent in 40-60year-olds and affects women more frequently, possibly due to variations in Q-angle. (4)

Symptoms of piriformis syndrome may begin abruptly as the result of a traumatic event or may develop slowly in response to repeated irritation. Piriformis muscle irritation and hypertonicity can result from a strain, a fall onto the buttocks or catching oneself from a “near fall.” In other instances, the process may begin following repetitive microtrauma, like long distance walking, stair climbing or from chronic compression, e.g, sitting on the edge of a hard surface or a wallet. (8,9)

Presenting complaints for piriformis syndrome include pain, paresthesia or numbness beginning in the gluteal region and radiating along the course of the sciatic nerve. Additional symptoms may develop from local trigger point referral into the proximal thigh, sacroiliac and hip regions. (9) Symptoms are often provoked by holding any one position for longer than 15-20 minutes, particularly prolonged sitting or standing. Positional changes may provide transient relief. Patients may report increasing discomfort when walking, running, stair climbing, riding in a car or arising from a seated position. Activities that involve hip internal rotation, like sitting cross-legged, may exacerbate symptoms. Patients with piriformis syndrome sometimes exhibit an antalgic gait. (10)

Palpable hypertonicity and tenderness over the piriformis muscle are hallmarks of clinical evaluation. (11,12) Tenderness from compensatory somatic dysfunction in the sacroiliac joint and associated hip musculature is likely. The obturator internus, located deep to both the piriformis muscle and sciatic nerve, is a synergistic hip external rotator and may be a co-contributor to piriformis syndrome. (13) Clinicians should also assess the tensor fascia lata, obturator externus, adductor and gluteal muscles, particularly in chronic cases. Motion palpation and orthopedic testing may reveal sacroiliac joint dysfunction and compensatory restrictions in the spine and lower extremity. (11) Clinicians should evaluate the arch of the foot and assess for the possibility of a leg length inequality.

The patient may display a slightly externally rotated hip while at rest (Piriformis sign) (15,16) Orthopedic evaluation may demonstrate painfully limited passive hip internal rotation (Freiberg sign). (11,16) FADIR test (flexion, adduction, and internal rotation) has relatively good sensitivity and specificity for piriformis syndrome and, when positive, is sometimes called the “Pace sign.” (17,18) The Beatty test may assist in the diagnosis of piriformis syndrome. The test is performed with the patient lying on the unaffected side and slightly abducting the affected leg a few inches off of the table. Reproduction of the chief complaint is suggestive of piriformis syndrome. (19)

Patients may exhibit a positive straight leg raise. Longstanding piriformis hypertonicity may lead to sciatic perineural adhesions with additional nerve tension signs. Neurologic evaluation of piriformis syndrome may reveal changes in sensation, reflex and motor strength. Sciatica of piriformis origin may present with weakness or atrophy in the distal (leg) musculature, but unlike lumbar radiculopathy, piriformis syndrome is generally not accompanied by proximal (thigh) weakness. (20)

The diagnosis of piriformis syndrome is based on an accurate history and physical exam. Radiographic imaging of a suspected soft tissue disorder is of limited benefit. (21) Advanced imaging may be an appropriate modality to rule out other sources of radicular complaints. (17) Diagnostic ultrasonography may show enlargement of the piriformis muscle belly producing compression on the sciatic nerve or anatomic variations in sciatic nerve location. Electrodiagnostic testing can help differentiate piriformis syndrome from lumbar radiculopathy. (20)

Piriformis syndrome shares several common characteristics and may even co-exist with other lumbopelvic problems. The differential diagnosis for piriformis syndrome includes: hip pathology; fracture; lumbar compression fracture; discitis; trochanteric bursitis; sacroiliitis; sacroiliac joint dysfunction; lumbar radiculopathy; spinal stenosis and viscerosomatic referred pain. (20,25,26)

The foundations of treatment for piriformis syndrome include stretching, myofascial release, and correction of underlying biomechanical dysfunction. Patients may need to temporarily limit provocative activities, including hill and stair climbing, walking on uneven surfaces, intense downhill running or twisting and throwing objects backward (i.e. firewood). Patients should avoid sitting on one foot and take frequent breaks from prolonged standing, sitting and car rides. Women should be cautious to limit sustained hip external rotation and abduction during gynecologic procedures or intercourse. (T&S). Stretching of the piriformis muscle is crucial and may be performed with seated, prone or quadruped maneuvers. (26)

Clinicians should be judicious in the application of soft tissue manipulation in order to avoid additional irritation to the sciatic nerve. Soft tissue release and stretching exercises may be appropriate for any associated myofascial concerns in the piriformis, gluteus, obturator, tensor fascia lata, hamstring, lumbar erectors, and hip adductors. Sciatic nerve flossing may be helpful. Manual manipulation may be necessary to correct lumbar, sacroiliac and lower extremity joint dysfunction. (28,29) Some studies have shown benefit from heat, ice, and ultrasound, particularly when applied prior to manual treatments. (30) NSAIDs may provide benefit in the early stages of management.

Strengthening exercises should be directed at the abductor, adductor and gluteal muscles. Clinicians should be alert to the possibility of lower crossed syndrome and formulate appropriate rehab plans to deal with any biomechanical dysfunction. Structural leg length inequalities may require the use of a heel lift. Patients with a loss of the longitudinal arch of the foot would benefit from arch supports or orthotics.

Medical co-management with muscle relaxants, steroids, trigger point injections or Botox may be considered for recalcitrant cases. (17,31)

References

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