The long thumb extensor
Extensor pollicis longus · musculus extensor pollicis longus
A forearm muscle that straightens the tip of your thumb and pulls it back.
What it does
Its tendon hooks around a small bump on the back of the radius and runs to the tip of the thumb. It straightens the thumb fully and pulls it back, as in a hitch-hiking gesture.
Surprising fact
This tendon can wear through and snap weeks after a wrist fracture, because it rubs over the healing bone at the bump where it changes direction.
Why it matters
If you suddenly can't lift your thumb after a broken wrist has healed, this tendon is the usual reason, and surgeons can repair it with a tendon transfer.
Nearby
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Sources
Drafted with AI help; awaiting a human fact-check against these sources.
Open in the 3D atlas · Suggest a correction · Not medical advice.
3D models: Z-Anatomy & BodyParts3D (CC BY-SA 4.0 / 2.1 JP). Card text CC BY 4.0.