Muscle
Extensor digitorum
Extensor shared by four fingers
High-yield
Its clearest direct action is extension at the finger MCP joints. Interphalangeal extension also depends on the extensor mechanism and the intrinsic hand muscles.
Overview
Four tendons carry this forearm muscle's pull onto the backs of the index, middle, ring and little fingers. The extensor expansions distribute that force across their joints.
Reference facts
- Origin
- Common extensor tendon attached to the humeral lateral epicondyle
- Insertion
- Extensor expansions of digits 2-5, continuing to their middle and distal phalanges
- Action
- Extends MCP joints of digits 2-5, contributes to IP extension, and assists wrist extension
- Innervation
- Posterior interosseous nerve, commonly C7-C8
- Blood supply
- Branches of the posterior interosseous artery
Clinical correlation
In mallet finger, injury to the terminal extensor tendon prevents active straightening of the fingertip. The injury may be a tendon tear or an avulsion that includes a small piece of bone.
Frequently asked questions
What does the extensor digitorum do?
The extensor digitorum extends MCP joints of digits 2-5, contributes to IP extension, and assists wrist extension.
What nerve innervates the extensor digitorum?
Posterior interosseous nerve, commonly C7-C8.
Where does the extensor digitorum attach?
The extensor digitorum originates from the common extensor tendon attached to the humeral lateral epicondyle and inserts on the extensor expansions of digits 2-5, continuing to their middle and distal phalanges.
What is the blood supply of the extensor digitorum?
Branches of the posterior interosseous artery.