Piriformis
Gluteal & Hip · Lower Limb
The piriformis is a pear-shaped muscle that is the most superior of the deep lateral rotators of the hip. It arises from the anterior (pelvic) surface of the sacrum around S2 to S4, passes out of the pelvis through the greater sciatic foramen, and inserts on the superior border of the greater trochanter of the femur. It laterally rotates the extended hip, abducts the flexed hip, and helps stabilise the hip joint by holding the femoral head in the acetabulum. It is supplied by the nerve to piriformis (S1, S2). The muscle is a key anatomical landmark in the gluteal region because the sciatic nerve usually passes just below it.
Origin, Insertion, Action & Nerve
Origin
Anterior (pelvic) surface of sacrum (S2–S4)
Insertion
Superior border of greater trochanter of femur
Action
Lateral rotation of extended hip; abduction of flexed hip; stabilizes hip joint
Nerve
Nerve to piriformis (S1, S2)
Attachments explained
The Piriformis is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.
Origin
Anterior (pelvic) surface of sacrum (S2–S4)
Insertion
Superior border of greater trochanter of femur
Action & function
When the Piriformis contracts, it produces the following movements: Lateral rotation of extended hip; abduction of flexed hip; stabilizes hip joint.
As part of the Gluteal & Hip group of the Lower Limb, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.
Nerve supply & clinical relevance
The Piriformis receives its nerve supply from the Nerve to piriformis (S1, S2). This nerve carries fibres from spinal segment(s) S1, S2.
Because a muscle can only contract when its nerve is intact, injury to the Nerve to piriformis or to its spinal roots (S1, S2) can weaken or paralyse the Piriformis, impairing the movements it normally produces (lateral rotation of extended hip). This is why knowing the innervation is central to localising nerve lesions in clinical practice.
How to study the Piriformis (the OIANS method)
Use the piriformis as your organising landmark for the gluteal region rather than memorising it in isolation. Because it exits through the greater sciatic foramen and the sciatic nerve typically emerges just beneath it, learning where the piriformis lies lets you locate the neurovascular structures above and below it in one step. Its rotation and abduction actions follow from its horizontal course to the greater trochanter.
Remember its changing action with hip position: it laterally rotates the extended hip but abducts the flexed hip, a shift that makes it a favourite exam point. Pair that with its close relationship to the sciatic nerve, which underlies the clinical idea of piriformis-related buttock and leg pain, to fix both function and significance together.
Frequently asked questions
Where is the Piriformis located?
The Piriformis is a muscle of the Gluteal & Hip group, located in the Lower Limb.
What is the origin of the Piriformis?
Anterior (pelvic) surface of sacrum (S2–S4)
What is the insertion of the Piriformis?
Superior border of greater trochanter of femur
What movements does the Piriformis produce?
Lateral rotation of extended hip; abduction of flexed hip; stabilizes hip joint
What nerve supplies the Piriformis?
Nerve to piriformis (S1, S2)
Is the Piriformis free to study in OIANS?
The Piriformis is always free to browse. Its full origin, insertion, action and nerve details are open to everyone in the Muscle Directory. Quiz and Flashcard practice for the Lower Limb is part of the one-time Lifetime upgrade, though; only the Upper Limb decks are free to test yourself on.
Related muscles
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