What action does the superior gemellus perform when the thigh is extended?

What action does the superior gemellus perform when the thigh is extended?

• A. Abducts a flexed thigh
• B. Laterally rotates an extended thigh
• C. Flexes thigh
• D. Medially rotates thigh

Answer: (B)

The superior gemellus is one of the external rotators of the hip. When the thigh is extended, its pull on the femur causes the leg to turn outward, or rotate laterally, at the hip joint. This lateral rotation is its primary action in an extended thigh, whereas flexed thigh can allow some abductive action, the classic function with the thigh extended is external rotation. The muscle works together with the obturator internus to rotate the femur laterally and help stabilize the hip by keeping the fem head centered in the acetabulum.

The superior gemellus is one of the external rotators of the hip. When the thigh is extended, its pull on the femur causes the leg to turn outward, or rotate laterally, at the hip joint. This lateral rotation is its primary action in an extended thigh, whereas flexed thigh can allow some abductive action, the classic function with the thigh extended is external rotation. The muscle works together with the obturator internus to rotate the femur laterally and help stabilize the hip by keeping the fem head centered in the acetabulum.