Lumbrical tendon

The lumbrical tendons are the distal extensions of the lumbrical muscles, playing a critical role in finger movement coordination. Unique among hand tendons, they originate directly from the tendons of the flexor digitorum profundus (FDP) within the palm, rather than from bone.

From their FDP origin, these slender tendons course around the lateral sides of the metacarpophalangeal (MCP) joints. They then extend to the dorsal aspect of the corresponding digits, where they insert into the extensor expansions (dorsal digital apparatus) of the fingers. This specific insertion allows the lumbrical tendons to facilitate their characteristic action: flexing the MCP joints while simultaneously extending the proximal and distal interphalangeal (PIP and DIP) joints.