Muscle Spotlight: The "Deep Six"

So far, we’ve taken a look at the gluteus maximus, gluteus medius, and gluteus minimus muscles and how important they are for the function of the hips, both in terms of stability and motion. There is one more set of muscles tucked away in the pelvis that is usually not addressed unless they start causing problems, though. If you’ve ever had the uncomfortable condition known as sciatica, you won’t want to miss this post!

The “deep six” muscles, as they are sometimes referred to, are actually a set of six lateral rotators of the hips. This group consists of the piriformis, the gemellus superior and gemellus inferior, the quadratus femoris, and the obdurator externus and obdurator internus. Together, these muscles all serve to turn the hip outwards, away from the midline of the body. You can see the action for yourself if you pretend to be a ballerina for a moment and try to rotate your legs outwards so that your feet are turned out in that classic ballet position. (Incidentally, this is why ballerinas and other dancers that hold their legs and hips in such a way tend to have very tight external rotators!)

All of the lateral rotators of the hip insert into or right next to the greater trochanter in some way, and they fan out to originate at various points around the sacrum and pelvis. An interesting thing to note about them is that five of the muscles are deep (beneath) the sciatic nerve, with only one of them sitting on top of it.* This muscle which deviates from its fellows is the piriformis, and it is often responsible for causing sciatica – painful inflammation of the sciatic nerve.

When the piriformis becomes too tight, it can pinch the sciatic nerve, leading to what can be excruciating pain for the sufferer. Fortunately, the piriformis can actually be addressed by massage therapists, helping to relax the muscle and alleviate the pain it is causing. An acute attack of sciatica may need to be dealt with in another fashion besides massage, as further compressing the already-irritated nerve may result in further inflammation and pain; but if the sciatica is a chronic annoyance, flaring up now and then only to die away and then make an unwelcome return, then massage and stretching may be excellent concurrent treatments.

Image courtesy of Trail Guide to the Body, Third Ed., by Andrew Biel

And that wraps up this series on the gluteal and deep pelvic muscles. I hope that it was informative and that it has perhaps changed the perspective of clients and therapists who were formerly reluctant to include gluteal work in their regular sessions. These muscles are not to be neglected, if at all possible, so show them some gratitude for all the hard work they do by having some extra work done on them every now and again. They will certainly thank you!

*Note: While the piriformis sits on top of the sciatic nerve in the vast majority of people, there are small percentages of the population for which this is not true. The nerve may split into its peroneal and tibial halves, with the former half passing above the piriformis and the latter half passing below it; or the peroneal portion may pass through the piriformis while the tibial portion passes below it. In an even smaller section of the population, the sciatic nerve may remain undivided, but instead of passing below the piriformis, will pass right through the center of it.