Lateral rotator group

The Lateral rotator group is a group of six small muscles in the hip which all externally (laterally) rotate the femur in the hip joint. It consists of the following muscles: Piriformis, gemellus superior, obturator internus, gemellus inferior, quadratus femoris and the obturator externus.

Anatomy

All six muscles of the lateral rotator group originate from the hip bone and attach to the upper part of the femur. The muscles are named for their actions, with the exception of the piriformis and the quadratus femoris which are named for their shapes.

Piriformis

The piriformis originates from the anterior (front) part of the sacrum, the part of the spine in the gluteal region, and from the superior margin of the greater sciatic notch (as well as the sacroiliac joint capsule and the sacrotuberous ligament). It exits the pelvis through the greater sciatic foramen to insert on the greater trochanter of the femur.

Gemellus superior

The Gemellus superior originates from the outer surface of the spine of the ischium. It is nearly parallel with the piriformis and attaches to the upper part of the greater trochanter of the femur.

Obturator internus

The obturator internus originates from the medial surface of the obturator membrane, the ischium near the membrane, and the rim of the pubis. It exits the pelvic cavity through the lesser sciatic foramen.

Gemellus inferior

The Gemellus inferior is the smallest of the three gemelli, and arises from the upper part of the tuberosity of the ischium, immediately below the groove for the obturator internus tendon. It blends with the lower part of the tendon of the obturator internus, and is inserted with it into the forepart of the trochanteric fossa.

Quadratus femoris

The quadratus femoris is a flat, quadrilateral skeletal muscle. It originates from the lateral margin of the ischial tuberosity and inserts into the quadrate tubercle on the intertrochanteric crest.

Obturator externus

The obturator externus is a flat, triangular muscle, which covers the outer surface of the anterior wall of the pelvis. It is sometimes considered part of the medial compartment of thigh, and sometimes considered part of the gluteal region.

Function

The primary function of the lateral rotator group is to laterally rotate the thigh at the hip joint. Other functions include stabilizing the hip joint and abducting the thigh when it is flexed.

Clinical significance

Injury or strain to the muscles of the lateral rotator group can cause pain and loss of mobility in the hip. This can be a result of overuse, trauma, or a specific condition such as Piriformis syndrome.

See also

• Hip muscles
• Hip joint
• Piriformis syndrome

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