Which forearm muscle is responsible for turning the hand inward while facing the palm downward?

The pronator muscle plays a crucial role in the movement of turning the hand inward, especially when the palm is facing downward. This action is known as pronation. The primary pronator muscle, the pronator teres, is located in the forearm and assists in rotating the radius over the ulna, thus enabling the hand to turn palm down.

This action is essential for various everyday tasks, such as using utensils or typing, where the orientation of the hand is important. While the biceps are involved in flexing the elbow and the triceps in extending it, they do not play a direct role in pronation. The supinator muscle, on the other hand, is involved in the opposite action—supination, which turns the palm upward. Therefore, the pronator muscle is correctly identified as the one responsible for this inward rotation of the hand when the palm is directed downward.