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The Extensor Indicis is in the Deep Layer of the Posterior Compartment of the forearm. It is also a member of the Deep Distal Four Group; the deep distal four group is composed of:
- Abductor pollicis longus
- Extensor pollicis brevis
- Extensor pollicis longus
- Extensor indicis
ATTACHMENTS:
- Posterior ulna to the index finger (finger #2).
- The proximal attachment is onto the distal 1/3 of the posterior ulna and interosseus membrane.
- The distal tendon of extensor indicis joins into the ulnar side of the distal tendon of the extensor digitorum going to the index finger.
ACTIONS:
- Extends the index finger at the metacarpophalangeal and proximal and distal interphalangeal joints.
- Extends and radially deviates the hand at the wrist joint.
- Supinates the forearm at the radioulnar joints.
NOTES:
- Other than the thumb, only the index and little fingers (fingers #2 and 5) have a second extrinsic extensor muscle. Having two extensor muscles allows the index finger to be so functional at physically pointing at and indicating things in the visual field.
- Both the extensor indicis and the extensor digiti minimi attach into the ulnar side of the distal tendon of extensor digitorum going to the respective finger.
