Palmar 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 palmar interossei muscles of the hand are unipennate and more volar in relation to the dorsal interossei. There are four muscles in this group, however the 1st is rudimentary and often considered part of either the adductor pollicis or the flexor pollicis brevis 1, 3 . They adduct the thumb, index, ring and little fingers along the long axis of the middle finger. Just like the dorsal interossei the tendons pass deep to the transverse metacarpal ligament.

  • Origin: Palmar surface of 1st, 2nd, 4th and 5th metacarpal bones
  • Insertion: Extensor hood and the base of the proximal phalange of their related digits
    • 1st: (often rudimentary) Base of proximal phalanx of thumb and extensor hood
    • 2nd: Medial side of extensor hood of index finger
    • 3rd &  4th Lateral side of ring and little fingers extensor hood and proximal phalanges, respectively
  • Innervation: Deep branch of the ulnar nerve (C8, T1)
  • Action:
    • Primary: Adduction of thumb, Index, ring and little fingers at the MCPJ joints. NB: the middle finger cannot adduct.
    • Secondary:  Contribute 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: 51551
Section: Anatomy
Synonyms or Alternate Spellings:

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