Which muscle is a prime mover for forearm pronation?

Which muscle is a prime mover for forearm pronation?

• A. Brachioradialis
• B. Triceps brachii
• C. Biceps brachii
• D. Pronator teres

Answer: (D)

Forearm pronation is produced by rotating the radius over the ulna to turn the palm downward. The muscle that primarily carries out this rotation is the pronator teres. It crosses the elbow and attaches to the radius, so when it contracts it pulls the radius across the ulna, turning the forearm into pronation. It also helps with elbow flexion. The other muscles listed don’t prime-pronate the forearm: brachioradialis mainly flexes the elbow, triceps brachii extends the elbow, and biceps brachii is a powerful supinator when the elbow is flexed. Hence, pronator teres best fits the role of the prime mover for forearm pronation.

Forearm pronation is produced by rotating the radius over the ulna to turn the palm downward. The muscle that primarily carries out this rotation is the pronator teres. It crosses the elbow and attaches to the radius, so when it contracts it pulls the radius across the ulna, turning the forearm into pronation. It also helps with elbow flexion.

The other muscles listed don’t prime-pronate the forearm: brachioradialis mainly flexes the elbow, triceps brachii extends the elbow, and biceps brachii is a powerful supinator when the elbow is flexed. Hence, pronator teres best fits the role of the prime mover for forearm pronation.