Which muscle is the primary extensor of the elbow joint?

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

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the function of the elbow joint, which primarily allows flexion and extension movements.
2. Step 2: Identify the muscles involved in moving the elbow joint. The main muscles to consider are the biceps brachii, brachialis, brachioradialis, and triceps brachii.
3. Step 3: Recall that the biceps brachii, brachialis, and brachioradialis are primarily responsible for flexion of the elbow joint, meaning they decrease the angle between the forearm and upper arm.
4. Step 4: Recognize that the triceps brachii is the muscle responsible for extension of the elbow joint, meaning it increases the angle between the forearm and upper arm by straightening the arm.
5. Step 5: Conclude that the primary extensor of the elbow joint is the triceps brachii, as it is the main muscle that performs elbow extension.