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Piriformis
A small deep muscle from the sacrum to the hip that rotates the thigh, and shares a doorway with the sciatic nerve.
Latin name: Musculus piriformis. In plain English, the deep rotator behind the hip, next to the sciatic nerve. It is filed here under hip and buttock.
Reference information, not a diagnosis. Where a symptom is described below, it is there so you can describe your own more precisely to a clinician — not so you can name what you have.
Where it is
Piriformis is the landmark muscle of the buttock. It arises inside the pelvis on the front of the sacrum, passes out through the greater sciatic foramen, and attaches to the top of the greater trochanter. Everything else that leaves the pelvis through that opening is described in relation to it — above it or below it — including the superior and inferior gluteal vessels and nerves, the pudendal nerve, and the sciatic nerve.
The sciatic nerve most often passes below the muscle. In a minority of people it splits, with part of it passing through the muscle belly, and there are several described variants. That anatomical relationship is the whole basis of the term piriformis syndrome.
| Feature | Detail |
|---|---|
| Origin | Anterior surface of the sacrum, around the second to fourth sacral segments |
| Insertion | Upper border of the greater trochanter of the femur |
| Nerve | Nerve to piriformis (S1-S2) |
| Main actions | External rotation of the extended hip; abduction when the hip is flexed toward a right angle |
What it does
With the hip extended it rotates the thigh outward, working with the other short external rotators — the gemelli, obturators and quadratus femoris. Once the hip is flexed to around ninety degrees, its line of pull changes and it becomes an abductor instead. It also helps hold the head of the femur in the socket.
Piriformis syndrome — buttock pain with sciatic-type symptoms attributed to this muscle irritating the nerve — is genuinely contested. It has no agreed diagnostic test, it overlaps with deep gluteal pain from several other structures, and lumbar spine causes are far more common. Buttock pain that runs down the leg deserves a proper assessment rather than a self-diagnosis and a lacrosse ball.
Exercises that load it
| Exercise | Category | Muscles the exercise library lists |
|---|---|---|
| Easy running (8 km/h) | Cardio | Legs, heart, lungs |
| Cycling (19-22 km/h) | Cardio | Quads, glutes, calves, heart |
| Brisk walking (5.5 km/h) | Cardio | Legs, heart |
| Lunges | Strength | Quads, glutes, hamstrings, balance |
It is loaded as part of the deep rotator group rather than trained alone. Single-leg work, lateral movement, and any running or cycling that involves controlling rotation of the thigh will involve it. Direct strengthening — banded external rotation, clamshells with the hip flexed — is a small addition rather than the main event.
How it is lengthened
A figure-four stretch, either seated with the ankle on the opposite knee or lying on the back with the thigh drawn in, is the standard one. Because piriformis changes function with hip angle, varying the amount of hip flexion changes what you feel. Stop short of any pain that radiates down the leg — that is a signal to have it assessed, not to push further.
When it goes wrong
| Problem | What it typically feels like | Usual setting |
|---|---|---|
| Deep gluteal pain | A deep ache in the buttock, worse on prolonged sitting, sometimes with pain into the back of the thigh | Prolonged sitting, hill running, or a sudden increase in load |
| Sciatic-type leg pain | Pain running down the back of the leg, sometimes past the knee, with tingling or numbness | Most often a lumbar nerve root problem rather than the piriformis muscle |
| Ischiofemoral or hamstring origin pain | Pain deep in the buttock near the sitting bone, worse with long strides or sitting on a hard chair | One of the several causes that overlap with what is loosely called piriformis syndrome |
Leg pain with weakness in the foot, numbness in the saddle area, or any change in bladder or bowel control is an emergency and needs immediate medical care.
Nothing on this page is a treatment plan. If a problem is limiting what you do, is not improving, or is getting worse, the right next step is an assessment by a doctor or a physiotherapist who can examine you.
Sources: descriptive anatomy from Gray's Anatomy of the Human Body, 20th US edition (1918), which is in the public domain; Latin names follow Terminologia Anatomica, published by the Federative International Programme for Anatomical Terminology. Nerve root levels are the conventional ranges taught from those sources and vary between individuals and between textbooks. Exercise cross-links use the TempoLife exercise library. Checked 2026-09-06.
Frequently asked questions
Is piriformis syndrome a real diagnosis?
It is a recognised label but a contested one. There is no agreed test for it, several other structures in the deep buttock cause identical symptoms, and lumbar spine causes are far more common. That is a reason to be assessed properly rather than to assume.
Where does the sciatic nerve run relative to piriformis?
In most people it passes underneath the muscle as it leaves the pelvis. In a minority, part of the nerve passes through the muscle, and several other variants have been described.
Does sitting on a wallet cause piriformis pain?
Sitting on anything bulky puts asymmetric pressure through the buttock and can be uncomfortable. It is an easy thing to change and costs nothing to try.
Nearby in this reference
Iliopsoas
The deep hip flexor that runs from the lower spine to the thigh
Gluteus maximus
The main buttock muscle
Gluteus medius
The side-hip muscle that keeps the pelvis level
Tensor fasciae latae
The small front-of-hip muscle that tightens the IT band
Hip adductors
The inner thigh muscles
Deltoid
The cap of the shoulder
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