Muscle
Extensor pollicis brevis
Straightens the thumb at the MCP joint
High-yield
Brevis usually reaches the proximal phalanx; longus reaches the distal phalanx. Brevis shares wrist compartment 1 with abductor pollicis longus.
Overview
This deep forearm muscle travels beside abductor pollicis longus to the thumb. Its usual insertion is on the proximal phalanx, so its main action is at the thumb's MCP joint.
Reference facts
- Origin
- Posterior radius and neighboring interosseous membrane, distal to the abductor pollicis longus origin
- Insertion
- Usually the dorsal base of the thumb's proximal phalanx; tendon connections vary
- Action
- Extends the thumb at the MCP joint and helps extend it at the CMC joint
- Innervation
- Posterior interosseous nerve, commonly C7-C8
- Blood supply
- Branches of the posterior interosseous artery
Clinical correlation
The first compartment is the site of De Quervain tenosynovitis. Variation in tendon slips and the internal separation of this compartment can matter when clinicians assess persistent symptoms.
Frequently asked questions
What does the extensor pollicis brevis do?
The extensor pollicis brevis extends the thumb at the MCP joint and helps extend it at the CMC joint.
What nerve innervates the extensor pollicis brevis?
Posterior interosseous nerve, commonly C7-C8.
Where does the extensor pollicis brevis attach?
Origin: Posterior radius and neighboring interosseous membrane, distal to the abductor pollicis longus origin. Insertion: Usually the dorsal base of the thumb's proximal phalanx; tendon connections vary.
What is the blood supply of the extensor pollicis brevis?
Branches of the posterior interosseous artery.