Board of Certification for the Athletic Trainer (BOC) Practice Test

Which muscle weakness could contribute to external rotation impairment in the hip?

1. Rectus femoris

2. Hamstrings

3. Obturator externus

4. Iliopsoas

The correct answer is: Obturator externus

The correct answer is obturator externus, as this muscle plays a significant role in external rotation of the hip. When the obturator externus is weak, it can lead to difficulty in performing external rotation effectively. This muscle, located on the outer side of the pelvis and inserting into the greater trochanter of the femur, is particularly important for stabilizing the hip during movements that require rotation, such as walking or running. Understanding the specific functions of each muscle is crucial for recognizing how weakness in one can affect overall movement. The rectus femoris primarily acts in flexing the hip and extending the knee, while the hamstrings are more involved in hip extension and knee flexion. The iliopsoas is predominantly responsible for hip flexion. Thus, while these other muscles contribute to various hip functions, they do not directly affect external rotation in the same way that weakness in the obturator externus would.