Which muscle is the primary extensor of the forearm at the elbow joint?

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

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the action of each muscle listed in the problem in relation to the elbow joint. The elbow joint primarily allows flexion and extension movements.
2. Step 2: Recall that the biceps brachii and brachialis muscles are primarily responsible for flexion of the forearm at the elbow, meaning they decrease the angle between the forearm and the upper arm.
3. Step 3: Recognize that the brachioradialis assists in flexion of the forearm, especially when the forearm is in a mid-pronated position (like a handshake position).
4. Step 4: Identify that the triceps brachii is the muscle responsible for extension of the forearm at the elbow joint, meaning it increases the angle between the forearm and the upper arm.
5. Step 5: Conclude that since the question asks for the primary extensor of the forearm at the elbow, the correct muscle is the triceps brachii.