Which muscle is a primary hip abductor?

• A. Iliopsoas
• B. Gluteus medius
• C. Adductor longus
• D. Piriformis

Answer: (B)

Hip abduction is the movement that pulls the thigh away from the midline at the hip joint. The muscle that does this most effectively is the gluteus medius. It sits on the outer surface of the ilium and inserts on the greater trochanter of the femur, so its contraction pulls the femur laterally, producing abduction. Beyond moving the thigh outward, the gluteus medius also stabilizes the pelvis when you stand on one leg, keeping the pelvis level during walking. Its anterior fibers can assist with medial rotation and flexion, while the posterior fibers assist with extension and lateral rotation, but its primary action is abduction. The other muscles listed don’t serve as the main hip abductors: iliopsoas flexes the hip, adductor longus adducts (and aids flexion), and piriformis mainly acts as a lateral rotator (and can contribute to abduction when the hip is flexed) rather than acting as the primary abductor.