Which action best describes the function of the dorsal interossei muscles in the hand?

• A. Abduct the index, middle, and ring fingers away from the midline
• B. Adduct the little finger toward the midline
• C. Flex the metacarpophalangeal joints of the index and middle fingers
• D. Extend the interphalangeal joints of the fingers

Answer: (A)

Dorsal interossei act as finger abductors, meaning they move digits away from the midline of the hand (the midline is defined by the middle finger). These muscles lie between adjacent metacarpals and attach to the extensor expansion and bases of the proximal phalanges of digits 2–4. When they contract, they pull these digits laterally away from the middle finger, producing abduction of the index, middle, and ring fingers. They also contribute to flexion at the metacarpophalangeal joints and assist with extension of the interphalangeal joints through the extensor mechanism, supporting grip and finger stabilization.

The other options describe actions not characteristic of the dorsal interossei: adduction toward the midline is the role of the palmar interossei; and while the interossei can influence MCP flexion and IP extension via the extensor mechanism, abduction is the primary, defining action of the dorsal interossei.