Which muscle is not a primary forearm pronator?

Which muscle is not a primary forearm pronator?

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

Answer: (D)

Forearm rotation relies on two opposing actions: turning the palm downward (pronation) and turning it upward (supination). The main muscles that pronate the forearm are the pronator teres and the pronator quadratus. Among the options, the one whose primary job is to rotate the forearm in the opposite direction—supination—is the supinator. It wraps around the radius and pulls it to rotate the palm upward, especially with the elbow extended. The other muscles listed aren’t primary pronators: flexor carpi radialis mainly flexes and radially deviates the wrist (not a primary forearm rotator), and brachioradialis primarily flexes the elbow and helps bring the forearm to a neutral position rather than driving pronation. So the muscle not serving as a primary forearm pronator is the supinator.

Forearm rotation relies on two opposing actions: turning the palm downward (pronation) and turning it upward (supination). The main muscles that pronate the forearm are the pronator teres and the pronator quadratus. Among the options, the one whose primary job is to rotate the forearm in the opposite direction—supination—is the supinator. It wraps around the radius and pulls it to rotate the palm upward, especially with the elbow extended. The other muscles listed aren’t primary pronators: flexor carpi radialis mainly flexes and radially deviates the wrist (not a primary forearm rotator), and brachioradialis primarily flexes the elbow and helps bring the forearm to a neutral position rather than driving pronation. So the muscle not serving as a primary forearm pronator is the supinator.