Palmar Interossei

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The Palmar Interossei muscles are members of the Central Compartment Group of intrinsic muscles of the hand, composed of the:

• Adductor pollicis
• Lumbricals manus
• Palmar interossei
• Dorsal interossei manus

There are three Palmar Interossei muscles, named #1, #2, and #3, from radial/lateral (thumb side) to ulnar/medial (little finger side).

ATTACHMENTS:

• The palmar interossei attach from metacarpals #2, #4, and #5 to the proximal phalanges of fingers #2, #4, and #5 on the “middle-finger side.”
  • Palmar interosseus #1 attaches onto finger #2 (index finger).
  • Palmar interosseus #2 attaches onto finger #4 (ring finger).
  • Palmar interosseus #3 attaches onto finger #5 (little finger).
  • The palmar interossei also attach distally into the dorsal digital expansion.

ACTIONS:

• Adducts fingers #2, #4, #5 at the metacarpophalangeal joints.
• Flexes fingers #2, #4, #5 at the metacarpophalangeal joints.
• Extends fingers #2, #4, #5 at the proximal and distal interphalangeal joints.

NOTES:

1. Because the palmar interossei attach onto their respective fingers on the “middle-finger side,” they bring those fingers toward the middle finger, which is defined as adduction.
2. There is a mnemonic for remembering the abductors/adductors of the fingers: DAB PAD – Dorsals ABduct Palmars ADduct.