During midstance, the hip GRF position is described as posterior in the sagittal plane and what in the frontal plane?

During midstance, the hip GRF position is described as posterior in the sagittal plane and what in the frontal plane?

• A. Lateral
• B. Medial
• C. Anterior
• D. Superior

Answer: (B)

Understanding how the ground reaction force (GRF) line of action relates to the hip joint in different planes gives you the torque the hip experiences during midstance. In midstance, the GRF line passes behind the hip in the sagittal view, which relates to a posterior placement. In the frontal plane, that same force is directed toward the midline of the body, i.e., medial to the hip joint center, producing a medial (adduction) torque. This medial orientation is what the statement refers to, and it’s why the hip abductors must counteract to keep the pelvis stabilized during single-leg support.

Understanding how the ground reaction force (GRF) line of action relates to the hip joint in different planes gives you the torque the hip experiences during midstance. In midstance, the GRF line passes behind the hip in the sagittal view, which relates to a posterior placement. In the frontal plane, that same force is directed toward the midline of the body, i.e., medial to the hip joint center, producing a medial (adduction) torque. This medial orientation is what the statement refers to, and it’s why the hip abductors must counteract to keep the pelvis stabilized during single-leg support.