It's kind of serendipitous that I start writing a thing about the lateral rotator muscles when a Lewis Black schtick comes on my iTunes about mixing up FEMA and femur.
The lateral rotators are muscles in the hip/gluteal region of the body and their main job is basically what it sounds like: to rotate the hip joint laterally. To a lesser extent, they also help with other motions of the hip, such as extension and adduction.
The lateral rotators in context and in action. Images and video footage from Muscle Premium.
The lateral rotators are: the superior gemellus, inferior gemellus, obturator externus, obturator internus, quadratus femoris, and the piriformis. These muscles all originate on the pelvic area and insert onto the greater trochanter of the femur.
Let's take a quick dive into each of them, shall we?
The piriformis is a long muscle that originates on the anterior surface of the lateral process of the sacrum and gluteal surface of the ilium at the margin of the greater sciatic notch. It inserts on the superior border of the greater trochanter.
Like the gemellus muscles, the piriformis rotates the hip laterally. If the thigh is flexed, it also helps to abduct it.
I love these two. They have such interesting shapes—they kind of look like comic book word bubbles if you turn your head and squint.
The externus originates on the external surface of the obturator membrane and the margins of obturator foramen (the hole created by the pubis and ischium); the internus originates on the inner surface of the obturator foramen and the surfaces of the surrounding bones. They insert onto the posteromedial surface of the greater trochanter.