The Piriformis Muscle

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What and where is the piriformis muscle?

The Piriformis Muscle

Many people have heard of the piriformis muscle because they’ve heard of piriformis syndrome or they’ve heard that the muscle can be associated with sciatica-like pain. But, what exactly is the piriformis muscle?

Where is the piriformis muscle located?

Piriformis is a pear-shaped muscle that’s located underneath the big gluteus maximus on the buttocks. It’s one of a group of six muscles that work together called the deep six lateral rotators of the hips.

Origin

The piriformis muscle originates on the anterior sacrum.

Insertion

The piriformis muscle inserts on the superior portion of the greater trochanter, which is a bony protrusion on the top of the femur or thigh bone.

An important fact about the location of the piriformis muscle is its location in relationship to the sciatic nerve. Most commonly, the piriformis muscle is located just superior to the sciatic nerve. Different orientations are also possible where some or all of the sciatic nerve runs through the piriformis muscle, which can be one contributing factor to piriformis syndrome.

What actions does the piriformis muscle do?

When we start describing the actions of piriformis, things get a little tricky. This is because the actions of piriformis depend on the position of the hip.

If the body is in anatomical position, then the movement of the piriformis muscle is pretty straightforward. In that case, the piriformis muscle acts to:

  • Externally/laterally rotate the femur (thigh) at the hip joint

Things get a little more complicated when we move out of anatomical position. When we flex the hip joint, we change the line of tension between the sacrum and the greater trochanter. Current research (Chaitow and DeLaney, 2011; Travell and Simon, 1993) suggests that:

When the hip joint is flexed to 90°, the piriformis muscle can act to:

  • Abduct the femur at the hip joint

And when the hip joint is flexed at least 60° and up to full flexion, the piriformis muscle can act to:

  • Internally rotate the femur at the hip joint

If you want to learn more about the piriformis muscle, check out the related article in our series on the piriformis: What Is Piriformis Syndrome? Oh, and by the way, we cover it in our online course!

References:

Chaitow, L. and J. DeLany. 2011. The Hip. In Clinical Application of Neuromuscular Techniques. Volume 2 (Second Edition).

Travell, J.G. and D.G. Simons. 1993. Piriformis and Other Short Lateral Rotators. In Myofascial Pain and Dysfunction —The Trigger Point Manual. Volume 2.