Which triangle-shaped muscle is a weak elbow extensor located lateral to the olecranon process?

• A. Anconeus
• B. Brachioradialis
• C. Flexor carpi radialis
• D. Triceps brachii

Answer: (A)

The main idea here is recognizing the small triangular muscle that acts as a helper elbow extensor and sits just lateral to the olecranon. This muscle is the anconeus. It provides a minor contribution to elbow extension, supplementing the larger triceps brachii, and is positioned right beside the olecranon on the lateral side, which fits the description of being located lateral to the olecranon process. Its origin is from the lateral epicondyle of the humerus and it inserts onto the lateral aspect of the olecranon and proximal ulna, allowing it to assist in extending the elbow and helping stabilize the joint during movement. Brachioradialis, flexor carpi radialis, and the triceps brachii do not fit as well: brachioradialis mainly flexes the elbow from a mid-pronation position; flexor carpi radialis acts as a wrist flexor on the anterior forearm; and while the triceps brachii is the primary elbow extensor, it is a larger muscle not described as a small triangle located just lateral to the olecranon.