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) | 
