Which muscle laterally rotates the hip?

• A. Vastus Medialis
• B. Biceps Femoris
• C. Gluteus Medius
• D. Gracilis

Answer: (B)

External rotation of the hip happens when the thigh turns outward in the hip socket, and the muscle that can contribute to this action among the options is the biceps femoris. Its long head crosses both the hip and knee joints, so when the knee is flexed, it can pull on the thigh in a way that rotates the femur outward. It also functions to extend the hip, but the rotation comes from its crossing the hip joint. The other muscles listed either acts mainly at the knee (vastus medialis), adduct the thigh (gracilis), or are primarily abductors with only limited rotational influence (gluteus medius). Therefore, the biceps femoris best fits the action of lateral rotation of the hip.