What Is Piriformis Syndrome?

The Piriformis: Anatomy and Function

The piriformis is a flat, pear-shaped muscle originating from the anterior surface of the sacrum (S2–S4 levels) and the superior aspect of the sacrotuberous ligament, passing through the greater sciatic foramen to attach to the superior aspect of the greater trochanter of the femur. Its primary action is external rotation of the hip in the anatomical position, transitioning to internal rotation and abduction as the hip moves into flexion beyond approximately 60 degrees. It also assists in stabilising the sacroiliac joint and contributes to deceleration of hip internal rotation during the loading phase of gait. Despite its relatively small size, the piriformis occupies a clinically significant anatomical territory — the deep gluteal space — through which the sciatic nerve and other neurovascular structures pass in close proximity.

How Does Piriformis Syndrome Develop?

Piriformis syndrome develops when the piriformis muscle becomes hypertonic, shortened, or directly traumatised, producing pain in the buttock and posterior hip region through myofascial mechanisms, and potentially irritating or compressing the sciatic nerve through proximity. Common precipitating factors include: prolonged sitting (particularly on hard surfaces or with hip external rotation as in cross-legged postures), which maintains the piriformis in a shortened position; direct trauma to the gluteal region (a fall, collision, or injection); lumbar or sacroiliac joint dysfunction that alters piriformis load and firing patterns; compensatory overactivation in the context of gluteal inhibition (where the piriformis is recruited as a substitute hip stabiliser when the gluteals are inhibited by pain or disuse); and sporting activities involving repetitive hip rotation such as rowing, swimming, and racquet sports.

The Relationship With the Sciatic Nerve

The anatomical relationship between the sciatic nerve and the piriformis varies considerably between individuals. In approximately 85–90% of people, the sciatic nerve exits the pelvis inferior to the piriformis through the infrapiriform foramen. In approximately 10–15% of individuals, one or both divisions of the sciatic nerve pass through the substance of the piriformis or superior to it — anatomical variants that substantially increase susceptibility to piriformis-mediated nerve compression. When a hypertonic piriformis compresses or irritates the sciatic nerve in its passage through the deep gluteal space, symptoms indistinguishable from radicular sciatica can be produced — buttock pain, posterior thigh aching, and neurological symptoms in the leg — in the absence of any spinal pathology.

Clinical Diagnosis

Piriformis syndrome is a clinical diagnosis. It should be suspected when buttock and posterior leg symptoms are reproduced by prolonged sitting, are associated with point tenderness deep in the gluteal region (over the mid-belly of the piriformis), and are provoked by tests that stretch or compress the piriformis. The FAIR test (Flexion, Adduction, Internal Rotation of the hip in supine) is the most commonly used provocation test, stretching the piriformis and reproducing sciatic-type symptoms when positive. The Beatty test (lying on the unaffected side and lifting the flexed knee off the table) activates the piriformis against resistance and reproduces deep gluteal pain. Direct palpation tenderness over the piriformis mid-belly (distinguishable from the more lateral tenderness of greater trochanteric bursopathy) supports the diagnosis. MRI or ultrasound may confirm piriformis hypertrophy or identify anatomical nerve variants in complex presentations.

Treatment Approach

Management of piriformis syndrome typically involves: soft tissue therapy directly to the piriformis using sustained compression, muscle energy techniques, and longitudinal release to reduce myofascial hypertonicity; dry needling to trigger points within the piriformis belly, which is particularly effective for the often deeply located taut bands; hip and lumbar mobilisation to address joint restriction contributing to altered piriformis loading; piriformis stretching (FAIR position) as a home exercise; and progressive gluteal strengthening — targeting the gluteus medius and maximus — to resolve the compensatory recruitment patterns that maintain piriformis overactivity. Identifying and modifying the precipitating postural or loading factor is essential: the piriformis will not settle while the patient spends eight hours daily in the position that perpetuates it.

Piriformis Syndrome vs True Sciatica

The clinical distinction from lumbar-origin sciatica is important because the management differs substantially. Features favouring piriformis syndrome over lumbar disc pathology include: buttock pain as the primary complaint (rather than back pain), pain worse with sitting rather than with lumbar flexion or extension, no lumbar provocation on orthopaedic testing, reproduction of symptoms with hip rotation rather than lumbar movement, and absence of neurological deficit (weakness, reflex change, dermatomal sensory loss). Features favouring lumbar origin include: low back pain as a primary feature, symptoms worsened by lumbar flexion or extension loading, positive straight leg raise reproducing symptoms below the knee, and neurological deficit in a dermatomal distribution. In practice, both may coexist — the piriformis may be hypertonic secondary to lumbar pathology, or both may independently contribute to sciatic-type symptoms.