Which muscle is the primary flexor of the elbow?

The primary flexor of the elbow is the brachialis muscle. This muscle is located underneath the biceps brachii and is the main driver of elbow flexion when the arm is in a neutral position. While the biceps brachii also contributes to elbow flexion, particularly when the forearm is supinated, the brachialis is considered the strongest and most effective flexor throughout a broader range of arm positions.

In contrast, the triceps brachii is primarily responsible for elbow extension, making it an antagonist to the flexors. The brachioradialis, though it does assist in elbow flexion, does not have the same level of primary responsibility as the brachialis, particularly since its action is more pronounced when the forearm is in a mid-position between supination and pronation. Therefore, the brachialis is clearly recognized as the primary muscle responsible for elbow flexion.