Follow and Like Us:

Extensor Indicis Anatomy: Origin, Insertion, Action

Extensor Indicis Anatomy Study

Extensor Indicis Anatomy
Origin:  Posterior surface of the ulna (distal to extensor pollicis longus) and the interosseous membrane
Insertion: Dorsal surface of the base of the middle phalanx and distal phalanx of the index digit
Action: Extension of the second digit (index finger)
Blood Supply: Posterior interosseous artery from the ulnar artery
Innervation: Radial nerve (C6, 7, 8)

Synergist: Extensor pollicis longus, Extensor digiti minimi

For pain and symptom information see: Extensor Indicis Pain and Symptoms


Primary Actions of the Extensor Indicis:

1. Extension of the second digit at the metacarpophalangeal joint

  • Agonists: Extensor Digitorum
  • Antagonists: First Dorsal Interosseous, First Palmar Interosseous, First Lumbrical, Flexor Digitorum Superficialis, Flexor Digitorum Profundus

2. Extension of the second digit at the proximal interphalangeal joint

  • Agonists: Extensor Digitorum, First Lumbrical, First Dorsal Interosseous, First Palmar Interosseous
  • Antagonists: Flexor Digitorum Superficialis, Flexor Digitorum Profundus

3. Extension of the second digit at the distal interphalangeal joint

  • Agonists: Extensor Digitorum, First Lumbrical, First Dorsal Interosseous, First Palmar Interosseous
  • Antagonists: Flexor Digitorum Profundus

Secondary Actions of the Extensor Indicis:

4. Assists with adduction of the second digit at the carpometacarpal joint

  • Agonists: First Palmar Interosseous
  • Antagonists: First Dorsal Interosseous


Basic Clinical Massage Therapy


Out of the scores of books in my office Basic Clinical Massage Therapy is by far the most referenced book in my library. The musculoskeletal system is overlaid on human models allowing you to learn the precise location, origin and insertions of each muscle. The models are pictured in various poses throughout the book which also helps you visualize muscles in motion and their actions relationship with the skeletal structure and other muscles. Though it is written for massage therapists, it is an excellent book for anyone who wants to learn about the muscular system. MT’s will benefit from recommended treatments for each muscle.

Anatomy Coloring Book


The Anatomy Coloring Book is one of the best study and reference books for beginning anatomy students. The diagrams are clearly labeled and allow you to see the relationship and placement of the various structures of the body. You will also be surprised how the act of coloring will help with recall. But this is not just a beginners book, it is also great for practitioners and therapists to have on hand to use with clients and patients to use as a visual reference.



The Trigger Point Therapy Workbook – Claire Davies, Amber Davies, and David G. Simons

Basic Clinical Massage Therapy: Integrating Anatomy and Treatment – James H. Clay and David M. Pounds

Trigger Point Therapy for Myofascial Pain – Donna Finando and Steven Finando