Dorsal Interossei Muscles of the Hand

The four dorsal interosseous muscles (dorsal interossei) are located between the metacarpals; the 1st dorsal interosseous muscle is easy to palpate; oppose the thumb firmly against the index finger and it can be easily felt. The four dorsal interossei abduct the fingers.

Acting together, the dorsal and palmar interossei and the lumbricals produce flexion at the metacarpophalangeal joints and extension of the interphalangeal joints (the so-called Z-movement). This occurs because of their attachment to the lateral bands of the extensor expansions.

See Also: Hand Anatomy, Bones & Muscles

Dorsal Interossei Muscles Anatomy

The 1st dorsal interossei muscle origins from the medial side of the proximal end of the first metacarpal and lateral side of the second metacarpal Lateral side of the base of the second proximal phalanx and the extensor expansion (Extensor Hood) and inserts on the lateral side of the base of the second proximal phalanx and the extensor expansion (Extensor Hood).

The 2nd dorsal interossei muscle origins from the medial side of the second metacarpal and lateral side of the third metacarpal and inserts on the lateral side of the base of the third proximal phalanx and the extensor expansion.

The 3rd dorsal interossei muscle origins from the medial side of the third metacarpal and lateral side of the fourth metacarpal and inserts on the medial side of the base of the third proximal phalanx and the extensor expansion.

The 4th dorsal interossei muscle origins from the medial side of the fourth metacarpal and lateral side of the fifth metacarpal and inserts on the medial side of the base of the fourth proximal phalanx and the extensor expansion.

The 4 dorsal interossei muscles are all innervated by the deep branch of ulnar nerve (C8 and T1). They also get their blood supply from the dorsal and palmar metacarpal arteries.

The dorsal interossei abduct the second, third and fourth digits. The first digit and the fifth digit have their own abductor muscles in the thenar and hypothenar eminence.

To test the dorsal interossei, the examiner holds adjacent extended and adducted fingers between thumb and middle finger, providing resistance as the individual attempts to abduct the fingers (the person is asked to “spread the fingers apart”).

References & More

1. Cael, C. (2010). Functional anatomy: Musculoskeletal anatomy, kinesiology, and palpation for manual therapists. Philadelphia, PA: Wolters Kluwer Health/Lippincott, Williams & Wilkins.
2. Moore, K. L., Dalley, A. F., & Agur, A. M. R. (2014). Clinically Oriented Anatomy (7th ed.). Philadelphia, PA: Lippincott Williams & Wilkins.
3. Valenzuela M, Bordoni B. Anatomy, Shoulder and Upper Limb, Hand Dorsal Interossei Muscle. [Updated 2023 Jul 17]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: Pubmed
4. Clinically Oriented Anatomy – 8th Edition