Name

# Extensor Indicis

Pronunciation

(eks-TEN-sor IN-di-sis)

Origin/Proximal Attachment

Postero-lateral surface of ulna (distal to extensor pollicis longus)

Interosseous membrane

Antebrachial fascia

Insertion/Distal Attachment

Base of middle & distal phalanx of index (2nd) finger

Action/Relevance

Extends 2nd digit (MCP & IP joints)

Adducts 2nd digit

Assists to extend the hand at the wrist

Stabilizes MCP joint for flexion of IP solely

Innervation

Radial nerve - posterior interosseous (C6, 7,8)

Notes

Extensor indicis is one of the deep muscles on the extensor aspect of the forearm. It originates from the:

* extensor surface of the ulna at a level between the middle and distal thirds

* adjacent interosseous membrane

It inserts into the extensor expansion of the index finger. At this point, it lies to the ulnar side of extensor digitorum.

It acts to:

* extend all the joints of the index finger

* assist wrist extension

Extensor indicis is innervated by the posterior interosseous nerve (C7,C8).