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

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

Answer: (C)

In measuring hip flexion, the moving arm must follow the thigh’s long axis. As the hip moves, the angle you’re tracking is between the pelvis (stationary arm) and the femur, so the moving arm should be aligned with the midline of the femur. Aligning it to the midline of the tibia or fibula would tie the measurement to the lower leg, not the hip, leading to an inaccurate reading. A lateral midline of the femur would deviate from the bone’s central axis and skew the angle as the leg moves. So the moving arm should be oriented along the midline of the femur.