Which muscle is the primary extensor of the elbow joint?

• A. Triceps brachii
• B. Brachioradialis
• C. Biceps brachii
• D. Brachialis

Answer: (A)

Verified step by step guidance

1. Understand the function of the elbow joint: it primarily allows flexion and extension movements, meaning bending and straightening of the arm.
2. Identify the muscles involved in these movements: muscles that cross the elbow joint can either flex (bend) or extend (straighten) the forearm.
3. Recall that the biceps brachii, brachialis, and brachioradialis are primarily involved in flexion of the elbow joint, meaning they help bend the arm.
4. Recognize that the triceps brachii is the main muscle responsible for extension of the elbow joint, meaning it straightens the arm by contracting.
5. Therefore, the primary extensor of the elbow joint is the triceps brachii muscle.