What and where are the deep six lateral rotator muscles?
The deep six lateral rotator muscles are often discussed as a group because they have the same primary action and they generally function together. We’ve already covered one of the deep six lateral rotator muscles, the piriformis muscle in a separate post. The piriformis muscle sometimes gets singled out of the group because it can be the culprit behind piriformis syndrome and can be associated with sciatica-like pain. But, what exactly is the deep six lateral rotator muscle group?
Which muscles are included in the deep six lateral rotator muscle group?
There are six muscles in this group as the name suggests. They include: piriformis, obturator internus, obturator externus, gemellus inferior, gemellus superior, and the quadratus femoris.
Where are the deep six lateral rotator muscles located?
All six of the muscles in this group originate somewhere on the pelvis and run laterally across the pelvis to attach to the greater trochanter. Let’s get more specific about the attachments for each of these muscles.
Origins
- The piriformis muscle originates on the anterior sacrum.
- The gemellus inferior and gemellus superior originate on the ischial spine.
- The obturator externus originates on the external surface of the obturator foramen.
- The obturator internus originates on the internal surface of the obturator foramen.
- The quadratus femoris originates on the ischial tuberosity.
Insertion
All six of the deep six lateral rotators insert on the greater trochanter of the femur.
What actions do the deep six lateral rotator muscles do?
Generally, recent research suggests the overall function of this group of muscles is for support and stability of the hip joint, rather than big movements. The overall job of the deep six lateral rotators is to keep the “ball” of the ball and socket joint (the greater trochanter of the femur) in the “socket” (the acetabulum of the pelvis) when we are walking, running or doing other movements (Yoo et al., 2015). Specifically, all six of these muscles laterally rotate the femur at the hip joint.
Researchers are still exploring whether some of these muscles also assist with other movements. As all of the deep six lateral rotators are located deep to at least one other muscle, it makes it more difficult to insert the electrodes for electromyography (EMG), which are typically used in the laboratory to determine muscle action.
Some researchers suggest that obturator internus gemellus inferior, and possibly gemellus superior, can assist with abduction of the thigh if the hip joint is flexed (Chaitow and DeLany, 2011; Yoo et al., 2015). Piriformis may also assist in abduction of the thigh when the hip is flexed and recent EMG analysis also suggests that it may contribute to extension of the hip (Yoo et al., 2015). Some researchers are now finding that quadratus femoris and obturator externus may assist with adduction of the thigh, depending on what position the leg is in (Yoo et al., 2015).
If you want to learn more about the deep six lateral rotator muscles, check out our related articles. If you want to learn more about the piriformis muscle specifically, check out the related articles in our series on the piriformis: The Piriformis Muscle and What Is Piriformis Syndrome.
References
Chaitow, L. and J. DeLany. 2011. The Hip. In Clinical Application of Neuromuscular Techniques. Volume 2 (Second Edition).
