Dorsal Interosseous Muscles Under the Skin, Dorsal View

Description

Seen through the dorsal skin of an adult male hand, the dorsal interosseous muscles occupy the intermetacarpal spaces between the first through fifth metacarpals, their bipennate fibers converging toward the radial sides of digits 2 through 4 and to digit 2 from the first web space. Proximal to the metacarpal heads, each belly lies deep to the extensor digitorum tendons and dorsal digital expansion, while remaining superficial to the palmar interossei and the metacarpal shafts. Distally, tendinous slips course toward the bases of the proximal phalanges and into the extensor hood at the metacarpophalangeal (MCP) joints. Clear boundaries define each web space. Functionally, dorsal interossei abduct the index, middle, and ring fingers away from the axial line of the third digit, and they also assist lumbricals in MCP flexion with interphalangeal extension through their insertion into the dorsal aponeurosis. That anatomy matters when localizing ulnar neuropathy: the deep branch of the ulnar nerve supplies these muscles, so weakness of finger abduction (a classic “DAB” finding) and first dorsal interosseous wasting in the first web space often point to compression in Guyon canal or injury during ulnar-sided wrist surgery. Their position between metacarpals also makes them relevant to deep space infections and to reconstructive planning around the first web space. Use this plate for upper-limb anatomy teaching when you need to contrast dorsal interossei with palmar interossei, or for hand surgery and sports medicine publications explaining intrinsic muscle testing, ulnar nerve lesions, and MCP joint biomechanics. It also fits occupational therapy and hand therapy materials focused on intrinsic strengthening and deformity patterns such as ulnar clawing. Anatomical accuracy verified by SciePro's Medical Advisory Board.