What is the primary action of the brachioradialis muscle at the elbow joint?

• A. Flexion of the forearm at the elbow, especially when the forearm is in a neutral (thumb-up) position
• B. Pronation of the forearm at the radioulnar joints
• C. Abduction of the arm at the shoulder joint
• D. Extension of the forearm at the elbow

Answer: (A)

Verified step by step guidance

1. Identify the anatomical location of the brachioradialis muscle: it originates on the lateral supracondylar ridge of the humerus and inserts near the styloid process of the radius.
2. Understand the primary function of the brachioradialis by considering its position relative to the elbow joint and forearm bones; it crosses the elbow joint anteriorly.
3. Recall that the brachioradialis acts mainly to flex the forearm at the elbow, especially when the forearm is in a neutral position (thumb pointing upward), which is different from pure flexors like the biceps brachii that work best with the forearm supinated.
4. Eliminate other options by matching muscle actions: pronation and supination are primarily performed by muscles like pronator teres and supinator, abduction occurs at the shoulder by deltoid, and extension at the elbow is performed by triceps brachii.
5. Conclude that the primary action of the brachioradialis is flexion of the forearm at the elbow joint, particularly when the forearm is in a neutral position.