Which muscle primarily extends the elbow?

• A. Biceps
• B. Triceps
• C. Brachialis
• D. Pronator teres

Answer: (B)

Elbow extension is produced mainly by the triceps brachii. This muscle has three heads that come together and insert on the olecranon of the ulna, which allows the forearm to straighten when it contracts. Other muscles crossing the elbow largely act as flexors rather than extensors. The biceps brachii and brachialis pull the forearm toward the upper arm to bend the elbow, while the pronator teres mainly pronates the forearm and assists with elbow flexion rather than extension. A small muscle called the anconeus can help stabilize and assist in extension, but the primary mover for straightening the elbow is the triceps brachii.