A Window into the Glutes: Anatomy lesson for the day.


A rather literal statement for a rather literal picture. Taken from the Human Body Exhibit at the Denver Museum of Science, this picture offers us a glimpse into, or in this case through, one of our favorite muscle groups. This group that we see here, is probably our second favorite group. They are often called the “deep six” and are the deep hip external rotators. If you count, you will notice there are only five….one remains unseen the obturator internus. More on that later.


See the linear white lines on the right of the window? That’ s the two portions of the sciatic nerve. Notice how it runs under the muscle at the top and over the others? The muscle it runs under is the famous piriformis. When this muscle gets tight, it can impinge the sciatic nerve, causing pain down the leg (known as sciatica). This represents one of many causes of pain radiating down the leg.


The next muscle south is the gemelli superior, then the obturator externus, gemelli inferior, and quadratus femoris. The sixth of the deep six is the obturator internus, which runs from the inside of the pelvis on the obtrobturator foramen (those huge “eyes” you see in an x ray when looking at a pelvis from the front) to a similar place on the femur.


A few observations you should make.


  • when someone chews your butt off, or chews you a new one, this picture gives it a whole new meaning

  • the sciatic nerve runs under the piriformis
  • The top (superior) five muscles have a tendonous insertion to the femur that you can see as a whitish area on the left

  • the last (or most inferior muscle) has a muscular insertion to the femur (which is a reddish area on the left)
  • the positioning of these muscles allows them to be external rotators of the femur when the foot is in the air

  • when the foot is planted, they become external rotators of the pelvis or can act to slow internal rotation of the femur during stance phase
  • as you proceed caudally, the muscles become stronger adductors of the thigh


We will see this post as a reference for some future posts on this most fascinating muscle groups. Until then, study up!


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