Extensor Digitorum Anatomy

Extensor Digitorum Muscle

Origin:  Lateral epicondyle of the humerus via the common extensor tendon
Insertion:  Main attachment: dorsal aspect of the base of the proximal phalanx of each of the four digits. Central slip: dorsal aspect of the base of the middle phalanx of each of the four digits. Lateral bands: via two slips to the dorsal aspect of the base of the distal phalanx of each of the four digits.
Actions: Extension of the fingers
Innervation: Radial nerve (C6 C7 C8)
Blood Supply: Posterior interosseous artery from the ulnar artery

Primary Actions of the Extensor Digitorum

1. Extension of the digits at the metacarpophalangeal joints

  Agonists:

  • Extensor Indicis (second digit)
  • Extensor Digiti Minimi (fifth digit)

  Antagonists:

  • Dorsal Interossei
  • Flexor Digiti Minimi (fifth digit)
  • Lumbricals (hand)
  • Palmar Interossei
  • Flexor Digitorum Profundus
  • Flexor Digitorum Superficialis

2. Extension of the digits at the proximal interphalangeal joints when metacarpophalangeal joints are flexed

  Agonists:

  • Dorsal Interossei
  • Palmar Interossei
  • Extensor Indicis (second digit)
  • Lumbricals
  • Extensor Digiti Minimi (fifth digit)

  Antagonists:

  • Flexor Digitorum Profundus
  • Flexor Digitorum Superficialis

3. Extension of the digits at the distal interphalangeal joints when metacarpophalangeal joints are flexed

  Agonists: 

  • Dorsal Interossei
  • Palmar Interossei
  • Extensor Indicis (second digit)
  • Lumbricals
  • Extensor Digiti Minimi (fifth digit)

  Antagonists:

  • Flexor Digitorum Profundus

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Secondary Actions of the Extensor Digitorum:

1. Assists with extension of the wrist with digits flexed at the metacarpophalangeal joints

  Agonists:

  • Extensor Carpi Radialis Longus
  • Extensor Carpi Radialis Brevis
  • Extensor Carpi Ulnaris

  Antagonists:

  • Flexor Carpi Radialis
  • Palmaris Longus
  • Flexor Carpi Ulnaris

2. Assists with abduction of the digits during extension of the carpometacarpal joints

  Agonists:

  • Dorsal Interossei
  • Extensor Digiti Minimi (fifth digit)

  Antagonists: Palmar Interossei