Courtesy: Prof Nabil Ebraheim, University of Toledo, Ohio, USA

 

Piriformis Syndrome – High Yield Orthopaedic Notes

Definition

• Piriformis syndrome is a neuromuscular condition caused by irritation or compression of the sciatic nerve by the piriformis muscle.
• It produces buttock pain and sciatic-type symptoms without primary lumbar spine pathology.
• Often mimics lumbar disc herniation and radiculopathy.

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Anatomy

Piriformis Muscle

Origin:
• Anterior surface of the sacrum

Insertion:
• Superior border of the greater trochanter

Action:
• External rotation of the hip in extension
• Abduction of the hip in flexion

Relationship to Sciatic Nerve

• Sciatic nerve usually passes beneath the piriformis muscle.
• Compression or irritation of the nerve can produce sciatica-like symptoms.

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Pathophysiology

Causes include:

• Muscle spasm
• Hypertrophy of piriformis
• Inflammation
• Trauma to the buttock
• Repetitive overuse
• Anatomical variations of the sciatic nerve

Result:

• Compression of the sciatic nerve
• Buttock pain
• Referred pain down the lower limb

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Clinical Features

Symptoms

• Deep buttock pain
• Pain radiating to the posterior thigh
• Occasionally pain extending below the knee
• Tingling or numbness in the leg
• Pain aggravated by:
• Sitting
• Climbing stairs
• Running
• Squatting

Clinical Clues

• Buttock pain predominates
• Symptoms often worsen with prolonged sitting
• Lumbar spine examination may be relatively normal

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Differential Diagnosis

Lumbar Disc Herniation

Features favoring disc disease:

• Low back pain
• Positive straight leg raise
• Neurological deficit
• MRI evidence of disc prolapse

Other Conditions

• Lumbar spinal stenosis
• Sacroiliac joint dysfunction
• Hamstring syndrome
• Ischiofemoral impingement
• Hip pathology

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Examination

Local Examination

• Tenderness over piriformis muscle in the buttock
• Reproduction of symptoms with stretching of the muscle

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Special Tests

Straight Leg Raise Test

Purpose:
• Primarily evaluates lumbar disc herniation

Positive Test:
• Reproduction of radicular pain

Interpretation:
• Strongly suggests lumbar nerve root irritation

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FAIR Test

(Flexion Adduction Internal Rotation Test)

Technique:
• Hip flexed
• Hip adducted
• Hip internally rotated

Positive Test:
• Reproduction of buttock pain or sciatic symptoms

Significance:
• Most commonly used test for piriformis syndrome

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Lasegue-Type Maneuver

Technique:
• Hip flexion with knee extension

Positive Test:
• Reproduction of sciatic symptoms

Indicates:
• Sciatic nerve irritation

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Important Distinction

FAIR Test

• Flexion
• Adduction
• Internal Rotation

Used for:
• Piriformis syndrome

FABER Test

• Flexion
• Abduction
• External Rotation

Used for:
• Sacroiliac joint pathology
• Hip pathology

Do not confuse the two tests.

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Diagnostic Features Supporting Piriformis Syndrome

• Buttock tenderness
• Positive FAIR test
• Symptoms reproduced by stretching piriformis
• Absence of significant lumbar pathology
• Normal or non-diagnostic spinal imaging

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Investigations

MRI Lumbar Spine

Purpose:
• Exclude disc herniation
• Exclude spinal causes of sciatica

MRI Pelvis

May demonstrate:
• Piriformis hypertrophy
• Muscle edema
• Anatomical variations

Electrophysiological Studies

Occasionally used to evaluate sciatic nerve involvement.

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Treatment

Conservative Management

First-line treatment:

• Activity modification
• NSAIDs
• Physiotherapy
• Stretching exercises
• Core strengthening
• Hip abductor strengthening

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Injection Therapy

Options:

• Local anesthetic injection
• Corticosteroid injection
• Ultrasound-guided piriformis injection

Purpose:

• Diagnostic
• Therapeutic

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Surgical Treatment

Rarely required

Indications:

• Persistent symptoms
• Failure of prolonged conservative treatment
• Confirmed sciatic nerve compression

Procedure:

• Piriformis release
• Sciatic nerve decompression

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Key Take Home Messages

• Piriformis syndrome is a cause of non-spinal sciatica.
• Buttock pain is the dominant symptom.
• FAIR test is the most useful clinical test.
• Always differentiate from lumbar disc herniation.
• Tenderness over the piriformis muscle supports the diagnosis.
• Most patients improve with conservative treatment.

Exam Pearls

• Piriformis originates from the anterior sacrum and inserts on the greater trochanter.
• Sciatic nerve compression by piriformis produces sciatica-like symptoms.
• FAIR test = Flexion + Adduction + Internal Rotation.
• FABER test evaluates hip and sacroiliac pathology, not piriformis syndrome.
• Positive straight leg raise is more suggestive of lumbar disc herniation.
• Piriformis syndrome remains a diagnosis of exclusion.

This format aligns well with your previous summaries on FABER test, Gaenslen test, straight leg raise test, and other orthopaedic examination maneuvers.