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Learn Muscle Anatomy: Lateral Rotators

Posted by Courtney Smith on Wed, Jan 02, 2013 @ 03:33 PM

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

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?

 

Superior and Inferior Gemellus

Superior and inferior gemellus

The superior gemellus and inferior gemellus are long, thin muscles that originate on the ischium and insert on the medial surface of the greater trochanter.

Both muscles, in addition to helping rotate the hip joint laterally, help to abduct the flexed thigh.

 

Piriformis

The piriformis

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.

 

Obturator Externus and Internus

lateral-rotator-muscles-obturators.png

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.

 

Quadratus Femoris

The Quadratus femoris

The quadratus femoris is a short, strong, rectangular muscle that originates on the ischial tuberosity and inserts onto the intertrochanteric crest.
 

That was kind of a lot of information to throw at you. Let's recap:

Muscle

Origin

Insertion

Action

Superior gemellus

Ischium

Medial surface of the greater trochanter

Laterally rotates hip joint

Inferior gemellus

Ischium

Medial surface of the greater trochanter

Laterally rotates hip joint

Piriformis

Anterior surface of the lateral process of the sacrum and the gluteal surface of the ilium at the margin of the greater sciatic notch

Superior border of the greater trochanter

Laterally rotates hip joint; abducts thigh when flexed

Obturator externus

External surface of the obturator membrane and the margins of obturator foramen

Trochanteric fossa

Laterally rotates hip joint; abducts thigh when flexed

Obturator internus

Internal surface of the obturator foramen and the surfaces of the surrounding bones

Posteromedial surface of the greater trochanter

Laterally rotates hip joint; abducts thigh when flexed

Quadratus femoris

Ischial tuberosity

Intertrochanteric crest

Externally rotates and adducts the hip joint

 


 

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Sources:

-          Muscle Premium

-          UW Radiology

-          Loyola University Medical