Which muscle is the primary hip extensor and external rotator?

• A. Gluteus maximus
• B. Psoas major
• C. Tensor fasciae latae
• D. Gluteus medius

Answer: (A)

The main muscle responsible for extending the hip and aiding external rotation is the gluteus maximus. It’s the largest buttock muscle, with fibers that pull the femur backward to extend the hip, especially when you’re moving against resistance (like standing up, climbing stairs, or powering through a run). Its posterior fibers tilt the thigh outward, giving it a notable external rotation component, particularly when the hip is flexed.

The other muscles in the list don’t fit as the primary extensor and external rotator. The psoas major is a powerful hip flexor, not an extender. The tensor fasciae latae mainly flexes, abducts, and medially rotates the hip and helps stabilize the knee via the iliotibial tract. The gluteus medius mainly abducts the thigh and stabilizes the pelvis, with some posterior-fiber contribution to external rotation but not the primary extensor or external rotator.