eMedicine Specialties > Physical Medicine and Rehabilitation > Lower Limb Musculoskeletal Conditions

Piriformis Syndrome

Author: Milton J Klein, DO, MBA, Consulting Physiatrist, Heritage Valley Health System-Sewickley Hospital, Allegheny General Hospital, and Ohio Valley General Hospital.
Contributor Information and Disclosures

Updated: Sep 14, 2009

Introduction

Background

Piriformis syndrome has been a controversial diagnosis since its initial description in 1928.1 The condition usually is caused by a neuritis of the proximal sciatic nerve. The piriformis muscle can either irritate or compress the proximal sciatic nerve due to spasm and/or contracture, and this problem can mimic a diskogenic sciatica. Piriformis syndrome is also referred to as pseudosciatica, wallet sciatica, and hip socket neuropathy.

Pathophysiology

The piriformis muscle is flat, pyramid-shaped, and oblique. This muscle originates to the anterior of the S2-S4 vertebrae, the sacrotuberous ligament, and the upper margin of the greater sciatic foramen (see image below and Image 1). Passing through the greater sciatic notch, the muscle inserts on the superior surface of the greater trochanter of the femur. With the hip extended, the piriformis muscle is the primary external rotator; however, with the hip flexed, the muscle becomes a hip abductor. The piriformis muscle is innervated by branches from L5, S1, and S2.

Nerve irritation in the herniated disk occurs at ...

Nerve irritation in the herniated disk occurs at the root (sciatic radiculitis). In piriformis syndrome, the irritation extends to the full thickness of the nerve (sciatic neuritis).

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Nerve irritation in the herniated disk occurs at ...

Nerve irritation in the herniated disk occurs at the root (sciatic radiculitis). In piriformis syndrome, the irritation extends to the full thickness of the nerve (sciatic neuritis).


A lower lumbar radiculopathy may cause secondary irritation of the piriformis muscle, which may complicate diagnosis and hinder patient progress.

Many developmental variations of the relationship between the sciatic nerve in the pelvis and piriformis muscle have been observed.2,3 In approximately 20% of the population, the muscle belly is split, with 1 or more parts of the sciatic nerve dividing the muscle belly itself. In 10% of the population, the tibial/peroneal divisions are not enclosed in a common sheath. Usually, the peroneal portion splits the piriformis muscle belly, although in rare cases, the tibial division does so.

Involvement of the superior gluteal nerve usually is not seen in cases of piriformis syndrome. This nerve leaves the sciatic nerve trunk and passes through the canal above the piriformis muscle.

Blunt injury may cause hematoma formation and subsequent scarring between the sciatic nerve and short external rotators. Nerve injury can occur with prolonged pressure on the nerve or vasa nervorum.

The etiology of piriformis syndrome can be divided into the following categories:

  • Hyperlordosis
  • Muscle anomalies with hypertrophy
  • Fibrosis (due to trauma)
  • Partial or total nerve anatomical abnormalities

Other causes can include the following:

  • Pseudoaneurysms of the inferior gluteal artery adjacent to the piriformis syndrome
  • Bilateral piriformis syndrome due to prolonged sitting during an extended neurosurgical procedure
  • Cerebral palsy
  • Total hip arthroplasty
  • Myositis ossificans
  • Vigorous physical activity

Piriformis syndrome remains controversial because, in most cases, the diagnosis is clinical, and no confirmatory tests exist to support the clinical findings.

Papadopoulos and colleagues proposed the following classifications for piriformis syndrome4 :

  • Primary piriformis syndrome - This designation would apply to piriformis syndrome resulting from intrinsic pathology of the piriformis muscle itself, such as myofascial pain, anatomic variations, and myositis ossificans.
  • Secondary piriformis syndrome (pelvic outlet syndrome) - This classification would encompass all other etiologies of piriformis syndrome, with the exclusion of lumbar spinal pathology.

Frequency

United States

Given the lack of agreement on exactly how to diagnose piriformis syndrome, estimates of the frequency of sciatica caused by piriformis syndrome vary from rare to approximately 6% of sciatica cases seen in a general family practice.5 Approximately 90% of adults have had at least 1 episode of disabling low back pain (LBP) in their lifetime.

Mortality/Morbidity

Piriformis syndrome is not life-threatening, but it can have significant associated morbidity. The total cost of low back pain and sciatica is significant, exceeding $16 billion in direct and indirect costs.

Sex

Some reports suggest a 6:1 female-to-male ratio for piriformis syndrome.

Clinical

History

Piriformis syndrome often is not recognized as a cause of low back pain (LBP) and associated sciatica. This clinical syndrome is due to a compression of the sciatic nerve by the piriformis muscle; it is identical in clinical presentation to LBP with associated L5, S1 radiculopathy due to diskogenic and/or lower lumbar facet arthropathy with foraminal narrowing. Not uncommonly, patients demonstrate both of these clinical entities simultaneously. This diagnostic dilemma highlights the need for patients with LBP and associated radicular pain to undergo a complete history and physical examination, including a digital rectal examination.

Many cases of refractory trochanteric bursitis are observed to have an underlying occult piriformis syndrome due to the insertion of the piriformis muscle on the greater trochanter of the hip. If a patient's trochanteric bursitis and piriformis syndrome are treated inadequately, both conditions remain resistant to medical management.

Physical

Examination findings may include the following:

  • Piriformis muscle spasm often is detected by careful, deep palpation.
  • A digital rectal examination may reveal a tenderness on the lateral pelvic wall that reproduces symptoms.
  • The reproduction of sciatica-type pain with weakness results from resisted abduction/external rotation (Pace test).
  • The Freiberg test is another diagnostic sign that elicits pain upon forced internal rotation of the extended thigh.6
  • The Beatty maneuver reproduces buttock pain by selectively contracting the piriformis muscle.7 The patient lies on the uninvolved side and abducts the involved thigh upward; this activates the ipsilateral piriformis muscle, which is a hip external rotator and, when the hip is flexed, an abductor.
  • A painful point may be present at the lateral margin of the sacrum.
  • Shortening of the involved lower extremity may be seen.
  • The patient may have difficulty sitting due to an intolerance of weight bearing on the buttock.
  • The patient may have the tendency to demonstrate a splayed foot on the involved side when in the supine position.
  • Piriformis syndrome alone is rarely the cause of a focal neuromuscular impairment; either a sciatic mononeuropathy or an L5-S1 radiculopathy can mimic both of these conditions, obscuring diagnosis of piriformis syndrome.
  • A Morton foot may predispose the patient to developing piriformis syndrome. The prominent second metatarsal head destabilizes the foot during the push-off phase of the gait cycle, causing foot pronation and internal rotation of the lower limb. As a compensatory mechanism, the piriformis muscle (external hip rotator) reactively contracts repetitively during each push-off phase of the gait cycle , leading to piriformis syndrome.

Causes

Approximately 50% of patients with piriformis syndrome have a history of trauma, with either a direct buttock contusion or a hip/lower back torsional injury. The remaining 50% of cases are of spontaneous onset, so the treating physician must have a high index of suspicion for the problem, lest it be overlooked.

More on Piriformis Syndrome

Overview: Piriformis Syndrome
Differential Diagnoses & Workup: Piriformis Syndrome
Treatment & Medication: Piriformis Syndrome
Follow-up: Piriformis Syndrome
Multimedia: Piriformis Syndrome
References
Further Reading
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References

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Further Reading

Related eMedicine topics:
 Botulinum Toxin in Pain Management
Chronic Pain Syndrome
Chronic Pelvic Pain
Injection, Piriformis
Nerve Entrapment Syndromes
Nerve Entrapment Syndromes of the Lower Extremity
Piriformis Syndrome [Sports Medicine]

Clinical guidelines:
Pain (chronic). Work Loss Data Institute - Public For Profit Organization. 2003 (revised 2008 May 19). 475 pages. NGC:006564

The initial management of chronic pelvic pain. Royal College of Obstetricians and Gynaecologists - Medical Specialty Society. 2005 Apr. 12 pages. NGC:004471

Clinical trials:
Effectiveness of Oral Prednisone in Improving Physical Functioning and Decreasing Pain in People With Sciatica

Ultrasound Description of the Sciatic Nerve

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Keywords

piriformis syndrome, sciatica, sciatic nerve, piriformis, sciatic, sciatic nerve pain, piriformis muscle, sciatic pain, sciatica treatment, sciatica exercises, nerve compression, sciatic nerve treatment, piriformis sciatica, pyriformis, pyriformis syndrome, hip socket neuropathy, pseudosciatica, wallet sciatica, deep gluteal syndrome

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Contributor Information and Disclosures

Author

Milton J Klein, DO, MBA, Consulting Physiatrist, Heritage Valley Health System-Sewickley Hospital, Allegheny General Hospital, and Ohio Valley General Hospital.
Milton J Klein, DO, MBA is a member of the following medical societies: American Academy of Disability Evaluating Physicians, American Academy of Medical Acupuncture, American Academy of Osteopathy, American Academy of Physical Medicine and Rehabilitation, American Medical Association, American Osteopathic Association, American Osteopathic College of Physical Medicine and Rehabilitation, American Pain Society, and Pennsylvania Medical Society
Disclosure: Nothing to disclose.

Medical Editor

Rajesh R Yadav, MD, Assistant Professor, Section of Physical Medicine and Rehabilitation, MD Anderson Cancer Center, University of Texas at Houston
Rajesh R Yadav, MD is a member of the following medical societies: American Academy of Physical Medicine and Rehabilitation
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: eMedicine Salary Employment

Managing Editor

Michael T Andary, MD, MS, Residency Program Director, Professor, Department of Physical Medicine and Rehabilitation, Michigan State University College of Osteopathic Medicine
Michael T Andary, MD, MS is a member of the following medical societies: American Academy of Physical Medicine and Rehabilitation, American Association of Neuromuscular and Electrodiagnostic Medicine, American Medical Association, and Association of Academic Physiatrists
Disclosure: allergan Honoraria Speaking and teaching; Pfizer Honoraria Speaking and teaching

CME Editor

Kelly L Allen, MD, Regional Medical Director, IMX-Medical Management Services
Disclosure: Nothing to disclose.

Chief Editor

Consuelo T Lorenzo, MD, Consulting Staff, Department of Physical Medicine and Rehabilitation, Alegent Health Care, Immanuel Rehabilitation Center
Consuelo T Lorenzo, MD is a member of the following medical societies: American Academy of Physical Medicine and Rehabilitation
Disclosure: Nothing to disclose.

 
 
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