Which muscle assists in both pronation and supination of the forearm?

• A. Flexor carpi radialis
• B. Supinator
• C. Pronator teres
• D. Brachioradialis

Answer: (D)

Verified step by step guidance

1. Understand the movements of pronation and supination: Pronation refers to the rotation of the forearm so the palm faces downward, while supination refers to the rotation of the forearm so the palm faces upward.
2. Review the function of the brachioradialis muscle: The brachioradialis is primarily a flexor of the elbow, but it also plays a role in assisting both pronation and supination when the forearm is in a neutral position (thumb pointing upward).
3. Compare the roles of the other muscles listed: The flexor carpi radialis is involved in wrist flexion and abduction, the supinator is specifically responsible for supination, and the pronator teres is specifically responsible for pronation. None of these muscles assist in both movements.
4. Identify the unique role of the brachioradialis: The brachioradialis helps stabilize the forearm during transitions between pronation and supination, making it the correct answer for a muscle that assists in both movements.
5. Conclude that the brachioradialis is the correct answer based on its dual role in forearm movement and its neutral positioning function during pronation and supination.