During midstance, which muscles provide frontal plane stability at the hip?

During midstance, which muscles provide frontal plane stability at the hip?

• A. Quadriceps
• B. Tibialis anterior
• C. Iliopsoas
• D. Gluteus medius/hip abductors

Answer: (D)

Frontal plane stability at the hip during midstance is provided mainly by the hip abductors, especially the gluteus medius (with help from the gluteus minimus). As you stand on one leg in midstance, the body’s weight creates lateral forces that tend to pull the pelvis toward the stance leg. The gluteus medius contracts to resist that inward pull, keeping the pelvis level and preventing excessive adduction of the femur. This action stabilizes the hip in the frontal plane and helps prevent a drop of the opposite pelvis, a movement pattern you’d see if these muscles were weak. The other muscles listed act in different ways or planes. The quadriceps are primarily knee extensors in the sagittal plane, not main contributors to hip frontal plane stability. The tibialis anterior influences the ankle (dorsiflexion and inversion) rather than the hip’s frontal plane control. The iliopsoas is a hip flexor, also mainly in the sagittal plane, and does not provide the abductor moment needed to stabilize the hip in the frontal plane.

Frontal plane stability at the hip during midstance is provided mainly by the hip abductors, especially the gluteus medius (with help from the gluteus minimus). As you stand on one leg in midstance, the body’s weight creates lateral forces that tend to pull the pelvis toward the stance leg. The gluteus medius contracts to resist that inward pull, keeping the pelvis level and preventing excessive adduction of the femur. This action stabilizes the hip in the frontal plane and helps prevent a drop of the opposite pelvis, a movement pattern you’d see if these muscles were weak.

The other muscles listed act in different ways or planes. The quadriceps are primarily knee extensors in the sagittal plane, not main contributors to hip frontal plane stability. The tibialis anterior influences the ankle (dorsiflexion and inversion) rather than the hip’s frontal plane control. The iliopsoas is a hip flexor, also mainly in the sagittal plane, and does not provide the abductor moment needed to stabilize the hip in the frontal plane.