Hip flexion ROM: which statement correctly identifies the moving arm orientation?

• A. Midline of tibia
• B. Midline of fibula
• C. Midline of femur
• D. Lateral midline of femur

Answer: (C)

When measuring hip flexion ROM, the moving arm should track the thigh’s long axis, since the thigh is the moving segment. Therefore, the moving arm is aligned with the midline of the femur. This orientation keeps the measurement focused on how far the hip can flex relative to the trunk, regardless of knee position. Aligning the moving arm with the tibia or fibula would tie the measurement to the lower leg and knee, which can vary with knee movement, and a lateral midline of the femur could introduce rotation bias. So, the midline of the femur is the correct orientation for the moving arm.