Which muscle primarily extends the index finger?

Which muscle primarily extends the index finger?

• A. Extensor Digitorum
• B. Abductor Pollicis Longus
• C. Extensor Pollicis Longus
• D. Extensor Indicis

Answer: (D)

Extending the index finger is done mainly by the extensor indicis. This muscle has a dedicated tendon to the index finger's extensor expansion, allowing independent extension at the finger’s joints. The extensor digitorum also helps extend the index finger, but its action is more general, reaching all the fingers (digits 2–5). The other two muscles act on the thumb, not the index finger: one extends and abducts the thumb, and the other extends the thumb itself. So the extensor indicis is the primary muscle for extending the index finger.

Extending the index finger is done mainly by the extensor indicis. This muscle has a dedicated tendon to the index finger's extensor expansion, allowing independent extension at the finger’s joints. The extensor digitorum also helps extend the index finger, but its action is more general, reaching all the fingers (digits 2–5). The other two muscles act on the thumb, not the index finger: one extends and abducts the thumb, and the other extends the thumb itself. So the extensor indicis is the primary muscle for extending the index finger.