The inferior gemellus does which action when the thigh is flexed?

The inferior gemellus does which action when the thigh is flexed?

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

Answer: (C)

The key idea here is how deep hip rotators change their action depending on hip position. The inferior gemellus, along with the superior gemellus and obturator internus, acts as a lateral rotator of the hip when the thigh is extended. But when the thigh is flexed, these same muscles shift to abduction of the flexed thigh. So, abducting a flexed thigh is the action you’d expect from the inferior gemellus in that position. The other movements don’t fit because lateral rotation is the role when the hip is extended, medial rotation isn’t characteristic of this muscle group, and active flexion isn’t its primary action when the hip is flexed.

The key idea here is how deep hip rotators change their action depending on hip position. The inferior gemellus, along with the superior gemellus and obturator internus, acts as a lateral rotator of the hip when the thigh is extended. But when the thigh is flexed, these same muscles shift to abduction of the flexed thigh. So, abducting a flexed thigh is the action you’d expect from the inferior gemellus in that position.

The other movements don’t fit because lateral rotation is the role when the hip is extended, medial rotation isn’t characteristic of this muscle group, and active flexion isn’t its primary action when the hip is flexed.