Piriformis tendon !
The piriformis tendon attaches to the top of the greater trochanter, the bony point of the outer hip.
Official name: Tendon of piriformis
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What it is
The tendon of the piriformis, attaching to the top of the greater trochanter.
What it does
Carries the pull of the piriformis to the femur to turn the thigh outward.
Key facts
- Attaches
- Upper border of the greater trochanter, often blending with the conjoint tendon of the obturator internus and gemelli
- Function
- Lateral rotation of the extended hip and abduction of the flexed hip; the sciatic nerve usually leaves the pelvis just below it
- Tight in
- Hip flexion, adduction and medial rotation (FAIR position)
Relations
- Above
- Gluteus medius and gluteus minimus; the superior gluteal vessels and superior gluteal nerve leaving above it
- Below
- Superior gemellus and obturator internus; the sciatic nerve emerging below it
- Superficial
- Gluteus maximus
- Deep
- Back of the hip capsule
How to find it
Not palpable as a separate structure: it lies deep to the gluteus maximus, running from the sacrum to the top of the greater trochanter; ultrasound shows it, with the sciatic nerve just below, for guided injections.
Examination
- FAIR test: buttock pain with the hip flexed, adducted and medially rotated
- Freiberg sign: buttock pain on passive medial rotation of the straight hip
- Pace sign: pain and weakness on resisted abduction and lateral rotation with the person seated
On imaging
MRI or MR neurography can show an enlarged muscle and the course of the sciatic nerve relative to it; ultrasound guides injections.
Common problems
- Piriformis syndrome: deep buttock pain, sometimes with sciatica-like pain down the leg, thought to come from the muscle irritating the sciatic nerve.
- Pain with long sitting.
- In some people the nerve passes through or above the muscle, a normal variation.
How it is diagnosed
Mostly by exam, after ruling out other causes such as a spinal disc problem. MRI of the spine and pelvis; sometimes a diagnostic injection.
Treatment
- Physical therapy with stretching and strengthening; avoiding long sitting.
- Ultrasound-guided injection into the muscle.
- Rarely, surgery to release the muscle when other treatment fails.
Clinical notes
- In deep gluteal syndrome the sciatic nerve may be trapped by the piriformis, the other short rotators or fibrous bands
- Image-guided injection into the piriformis (local anaesthetic, corticosteroid or botulinum toxin) is used both to treat and to support the diagnosis of piriformis syndrome
- A posterior hip dislocation often tears the piriformis and the other short rotators and can stretch the sciatic nerve beneath them, mostly its fibular division
Anatomical variants
- The sciatic nerve or its common fibular part passes through or above the muscle in a minority, about 1 in 5 in many series (figures vary)
- The muscle may fuse with the gluteus medius or gluteus minimus
Memory aid
Short external rotators, top to bottom: 'P-GO-GO-Q' (Piriformis, Gemellus superior, Obturator internus, Gemellus inferior, Obturator externus, Quadratus femoris).
Test yourself
Think of the answer, then tap the question to see it.
Where does the piriformis tendon insert?
On the upper border of the greater trochanter, often blending with the conjoint tendon of the obturator internus and gemelli.
Which structures leave the pelvis above the piriformis?
The superior gluteal vessels and the superior gluteal nerve.
Which nerves leave the pelvis below the piriformis?
The sciatic, inferior gluteal, pudendal and posterior femoral cutaneous nerves.
Which position does the FAIR test use for piriformis syndrome?
Hip flexion, adduction and internal (medial) rotation; buttock pain is positive.
Educational information, not medical advice. For any symptom, see a health professional.
Its names
- Official Latin (TA2)
- musculus piriformis TA2 2604
- Official Spanish (DeCS)
- Tendón del piriforme DeCS D013710
- English (TA2)
- Tendon of piriformis
Related
Sources: Terminologia Anatomica (TA2); DeCS; Anatomy, Bony Pelvis and Lower Limb: Piriformis Muscle.
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Representative model, for educational purposes only.
