Lumbrical Muscles Beneath the Skin, Dorsal View

Description

Dorsal integument has been removed to expose the intrinsic lumbrical muscles and their slender tendons as they course distally toward the extensor expansion over the metacarpophalangeal joints. Each lumbrical lies on the radial side of its corresponding finger ray, passing anterior to the deep transverse metacarpal ligament and then turning dorsally to blend into the dorsal digital aponeurosis alongside the extensor digitorum tendon. The metacarpals, proximal, middle, and distal phalanges, and the MCP and interphalangeal joint lines provide clear osseous landmarks for where the lumbrical contribution joins the central slip and lateral bands. Although the lumbricals originate from the flexor digitorum profundus tendons in the palm, their insertion into the extensor hood makes them mechanically relevant on the dorsum where finger posture is set. They flex the MCP joints while extending the PIP and DIP joints, so loss of lumbrical function in ulnar and median nerve palsies drives the intrinsic minus pattern and the classic clawing that becomes most obvious in the ring and little fingers. Small muscle, large consequence. Hand anatomy instructors will find this dorsal perspective useful when teaching the extensor mechanism, because students can trace how intrinsic tendons interface with the extensor expansion rather than treating the lumbricals as purely palmar structures. The plate also suits operative education for tendon balance procedures (for example, intrinsic release, lumbrical transfer, or extensor hood repair) and for explaining clinical exam findings such as the lumbrical plus finger after flexor tendon injury or adhesions. Anatomical accuracy verified by SciePro's Medical Advisory Board.