Video: Extensor pollicis longus muscle

Ever wondered what muscles are contracting when you give a thumbs up?! Well today we’re going to learn about one of the muscles which contributes to that movement. It’s the extensor pollicis longus muscle!

This muscle arises from the posterior middle third of the ulna and adjacent interosseous membrane. It extends distally all the way down to the tip of the thumb to insert onto the posterior base of the 1st distal phalanx.

When this muscle contracts, it extends the thumb at the metacarpophalangeal and interphalangeal joints, creating that signature thumbs up curve at the tip of your thumb!

Supplying the motor innervation to this muscle, enabling its movements is a branch of the radial nerve, the posterior interosseous nerve.