The origin of the supinator includes which structures?

• A. Medial Epicondyle of Humerus and Ulnar Collateral Ligament
• B. Lateral Epicondyle of Humerus and Annular Ligament
• C. Coronoid Process of Ulna and Interosseous Membrane
• D. Olecranon and Interosseous Membrane

Answer: (B)

The key idea is where the supinator attaches at its origin. This muscle wraps around the proximal radius, and part of its origin comes from structures on the outer elbow: the lateral epicondyle of the humerus and the annular ligament that surrounds the radial head. Those two attachments form the humeral and ligamentous basis of the muscle’s origin as it curves to wrap around the radius and insert proximally. It’s worth noting that the supinator also has a deep part that originates from the ulna (supinator fossa and crest), which isn’t captured by the other options. The other site pairs listed don’t align with the actual attachments of the supinator, so the combination of the lateral epicondyle and annular ligament best fits its origin.