What is the proximal reference line for Forearm Supination?

• A. midline forearm
• B. midline humerus
• C. anterior surface of humerus
• D. lateral epicondyle

Answer: (B)

The rotation measured as forearm supination is taken with the proximal segment fixed to the arm, so the proximal reference line should run along the humerus. Aligning the proximal arm of the goniometer with the midline of the humerus provides a stable, consistent axis on the upper arm, while the distal arm follows the forearm’s midline. This setup makes the measured angle reflect how much the forearm rotates around the radioulnar joints, typically with the elbow flexed around 90 degrees. Using the midline of the forearm as the proximal reference would misrepresent the movement, and using an anterior surface of the humerus or a landmark like the lateral epicondyle wouldn’t give a stable, reproducible reference line for this motion.