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

• A. Biceps brachii
• B. Deltoid
• C. Gluteus maximus
• D. Triceps brachii

Answer: (A)

Verified step by step guidance

1. Identify the joint involved in the movement: the elbow joint, which primarily allows flexion and extension of the forearm.
2. Recall the main muscles that act on the elbow joint: the biceps brachii, brachialis, brachioradialis (flexors), and the triceps brachii (extensor).
3. Understand the action of each muscle: the biceps brachii is known for flexing the forearm at the elbow and also supinating the forearm; the triceps brachii extends the forearm; the deltoid acts on the shoulder; the gluteus maximus acts on the hip.
4. Determine which muscle is the primary flexor by considering which muscle's main function is to decrease the angle at the elbow joint, which is the biceps brachii.
5. Conclude that the biceps brachii is the primary flexor of the forearm at the elbow joint based on its anatomical position and function.