Where does the extensor indicis tendon attach?

Where does the extensor indicis tendon attach?

• A. Ulna and interosseous membrane, extensor hood of digit 2
• B. Humerus and lateral epicondyle
• C. Scaphoid and trapezium
• D. Radius and interosseous membrane

Answer: (A)

The extensor indicis tendon comes from the posterior surface of the ulna and the adjacent interosseous membrane, and it inserts into the extensor hood (expansion) of the index finger. This arrangement lets the index finger be extended independently by pulling on the extensor expansion, separate from the main extensor digitorum tendons. Other options misplace the origin on the humerus, carpal bones, or radius, which does not describe the true origin and insertion of this tendon.

The extensor indicis tendon comes from the posterior surface of the ulna and the adjacent interosseous membrane, and it inserts into the extensor hood (expansion) of the index finger. This arrangement lets the index finger be extended independently by pulling on the extensor expansion, separate from the main extensor digitorum tendons. Other options misplace the origin on the humerus, carpal bones, or radius, which does not describe the true origin and insertion of this tendon.