Muscle
Lumbricals (hand)
Coordinate a bent knuckle with straighter finger joints
High-yield
The index and middle lumbricals usually use the median nerve; the ring and little lumbricals usually use the deep ulnar branch.
Overview
These four small muscles begin on deep finger-flexor tendons rather than on bone. They join the extensor expansions, helping combine MCP flexion with IP extension in digits 2–5.
Reference facts
- Origin
- Flexor digitorum profundus tendons for digits 2–5
- Insertion
- Radial side of each extensor expansion in digits 2–5
- Action
- Assist knuckle flexion and interphalangeal extension in the four fingers
- Innervation
- First and second: median nerve; third and fourth: deep ulnar branch, mainly C8–T1
- Blood supply
- Mainly the superficial palmar arch, with additional palmar arterial contributions
Clinical correlation
Weakness of the ulnar-supplied lumbricals together with the interossei can allow the ring and little fingers to claw: their MCP joints extend while their IP joints bend.
Frequently asked questions
What do the lumbricals (hand) do?
Assist knuckle flexion and interphalangeal extension in the four fingers.
What nerve innervates the lumbricals (hand)?
First and second: median nerve; third and fourth: deep ulnar branch, mainly C8–T1.
Where do the lumbricals (hand) attach?
The lumbricals (hand) originate from the flexor digitorum profundus tendons for digits 2–5 and insert on the radial side of each extensor expansion in digits 2–5.
What is the blood supply of the lumbricals (hand)?
Mainly the superficial palmar arch, with additional palmar arterial contributions.