When the hip is extended, which action is primarily performed by the piriformis?

When the hip is extended, which action is primarily performed by the piriformis?

• A. Laterally Rotates an Extended Thigh
• B. Abducts a Flexed Thigh
• C. Flexes the Thigh
• D. Adducts the Thigh

Answer: (A)

When the hip is extended, the piriformis acts as a lateral rotator of the thigh. Its fibers run from the anterior sacrum to the greater trochanter, crossing the hip joint in a way that, with the leg straight, pull the femur to turn outward. This external rotation is true for extension, whereas with a flexed hip the same muscle more often contributes to abduction. It does not primarily flex or adduct the thigh in this extended position, which is why lateral rotation of the extended thigh is the primary action.

When the hip is extended, the piriformis acts as a lateral rotator of the thigh. Its fibers run from the anterior sacrum to the greater trochanter, crossing the hip joint in a way that, with the leg straight, pull the femur to turn outward. This external rotation is true for extension, whereas with a flexed hip the same muscle more often contributes to abduction. It does not primarily flex or adduct the thigh in this extended position, which is why lateral rotation of the extended thigh is the primary action.