Upper limb

Second Lumbrical

Musculus lumbricalis II manus

Origin

Radial side of the tendon of flexor digitorum profundus to the middle finger (no bony attachment)

Insertion

Radial side of the extensor hood and proximal phalanx of the middle finger

Function

Flexion of the MCP joint with simultaneous extension of the IP joints of the middle finger

Innervation

Median nerve

Movement & chain

Together with the second dorsal and first palmar interossei, enables the combined MCP flexion/IP extension of the middle finger, such as when holding a pen while writing.

Palpation

Palpable on the radial side of the 3rd ray deep in the palm during MCP III flexion with IP extension.

Clinical

Innervated by the median nerve; crucial for middle finger intrinsic plus posture and fine manipulation.

Segmental innervation

Median nerve, C8-T1.

In clinical practice

Here too, the origin shown (metacarpal bone) is a bony approximation of the actual tendinous attachment.

Region in the model

Upper limb