Dorsal Interossei muscles (hand)

The interossei muscles, as a group consist of four palmar (1st is often rudimentary) and four dorsal muscles. Collectively the interossei contribute to abduction and adduction of the fingers and also contribute to flexion of the metacarpophalangeal joints (MCPJ) and extension of the interphalangeal joints (IPJ) through their insertion to the extensor hood. The reference axis through which abduction and adduction occurs is the long axis of the 3rd phalanx (middle finger).

The dorsal intrinsic muscles of the hand are bipennate and are the most dorsally situated of all intrinsic muscles of the hand. They are associated with abduction of the index, middle and ring fingers and the tendons run dorsally to the deep transverse metacarpal ligament.

  • Origin: Contiguous (adjacent) sides of the five metacarpal bones
  • Insertion: Extensor hood of their related digit and the base of the proximal phalanx
    • 1st: Largest – lateral side of index finger
    • 2nd & 3rd: Both attach to either side of middle finger
    • 4th: medial side of ring finger
  • Innervation: Deep branch of the ulnar nerve (C8,T1)
  • Action:
    • Primary: Abduction of index middle and ring fingers at the MCPJ joints. The middle finger can abduct both medially and laterally.
    • Secondary:  Contributes to the flexion of MCPJ and extension of the proximal interphalangeal joint and Distal interphalangeal joint. 

The pneumonic “PAD” and “DAB” can be used to help remember the different functions of the two muscle groups.

Palmar = ADdution

Dorsal = Abduction

Upper limb anatomy
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Article Information

rID: 51550
Section: Anatomy
Synonyms or Alternate Spellings:

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