Which muscle is the primary elbow flexor regardless of forearm position?

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

Answer: (A)

When the goal is elbow flexion that remains strong no matter how the forearm is rotated, the key muscle is the brachialis. It is a pure elbow flexor that attaches to the ulna, pulling straight on the elbow joint without involving the forearm bones. Because its pull doesn't rely on the radius or forearm position, it remains the primary elbow flexor in pronation, neutral, and supination.

Other muscles contribute depending on forearm position: the biceps brachii is particularly powerful when the forearm is supinated, and less so in pronation; the brachioradialis is strongest in neutral but isn’t the main flexor across all positions; the pronator teres mainly pronates and only assists elbow flexion to a minor extent.