The piriformis muscle.

Is there a more notorious muscle in yoga than the piriformis muscle? How did this relatively small muscle get the blame for so many ailments centered in our buttocks and legs? Can just one muscle really be that tight? And if it is, do we really need to maximally stretch it in poses such as pigeon, minute after minute, day after day?

The piriformis muscle starts on the anterior, or front facing, part of the sacrum. It is a rather small muscle, that is more broad at the sacrum, and gradually narrows before it inserts on the femur, at the top of the great trochanter.

What does it do? First, remember that in order for a muscle to perform an action, it contracts, or shortens. The piriformis muscle moves the femur into external rotation (sometimes referred to as lateral rotation) when your hip is straight, such as when you are standing. This is the motion you perform when you turn your leg to the right if you want to move to your right. You externally rotate at the hip joint and then move in that new direction.

When your hip is flexed or bent, as it would be in sitting, the piriformis moves your femur into abduction, or away from your body. If you were in a long sitting position (like dandasana), and wanted to bring your legs outward for wide-angled sitting pose, you would move your legs into abduction, or away from the midline of your body.

The piriformis is not the only hip external rotator. The largest muscle that performs external rotation is your gluteus maximus. The other muscles that do this motion include the gemellus inferior and superior, the quadratus femoris, and the obturator internus.

the sciatic nerve normally runs beneath the piriformis muscle. See the contributions to the sciatic nerver from multiple nerve roots from the spine.

The structure that lives under your piriformis is the main culprit in giving your piriformis its notoriety; the sciatic nerve. The sciatic nerve does not run through the piriformis, as is sometimes mistakenly taught in yoga teacher training programs (this happened to me). It is possible that a variation in some people’s anatomy can result in the nerve piercing the muscle, but this is rare, with an incidence rate of somewhere between 6-16% (Khan, 2018). Does this anomaly make someone more prone to piriformis pain? Yes. But this alone does not mean you will have piriformis syndrome. It is actually possible to have this anatomic variation and never experience any symptoms at all.

So is the piriformis really your pain generator? It can be. But this region is complex, and both the lumbar intervertebral disks as well as the sacroiliac joint are known to refer pain to this area. Injured hip labrums and pelvic floor problems can also cause deep aching in the buttocks that mimic piriformis pain. In some of these instances, doing a deep pigeon pose can make the problem worse, rather than correcting it. This is also true of deep forward folds, and prolonged hamstring stretching. Sometimes, taking the pressure off of these structures is what is needed. Some poses that allow the piriformis to shorten, include baby cobra, sphinx pose, locust pose, and other front body openers. When you lengthen the front of the body and allow the back body to shorten, your piriformis can shorten and relax.

If you or your students have ongoing pain in the area of the buttock, and it does not seem to be improving, despite stretching and strengthening, it is time for a physical therapist to have a look. It is rarely a one-stretch solution or one-activity restriction that solves the problems in this region.

References
Khan,D. Nelson,A. Piriformis Syndrome. Essentials of Pain Medicine (Fourth Edition), 2018.

Miller, T. A., et al. The diagnosis and management of piriformis syndrome: myths and facts. Can J Neurol Sci. 2012;39(5): 577–583.