What is the Extensor Pollicis Longus?

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  • Written By: Alex Paul
  • Edited By: Jacob Harkins
  • Last Modified Date: 17 August 2019
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The extensor pollicis longus is a muscle located in the forearm. The primary action of the muscle is to help extend the wrist as well as the thumb during a variety of different activities. Visually it’s possible to see the muscle at the bottom of the thumb. It is a much bigger muscle than its cousin the extensor pollicis brevis.

The origin of the extensor pollicis longus is on the ulna, which is a bone in the forearm. From around halfway between the elbow and the wrist, the muscle begins and then runs down the arm and up through the thumb before attaching to the distal phalanx. Its innvervation is from the posterior interosseous nerve. The antagonists of the muscle are the flexor pollicis longus and flexor pollicis brevis which help to counteract its movements.

The extensor pollicis longus muscle is long and thin in shape. At the base of the thumb, however, it forms a triangle shape in between two different tendons. The muscle starts off thicker and becomes thinner as it travels down the arm before entering the thumb. To view the extensor pollicis longus a person must look on the wrist’s radial side.


The muscle's main action is to extend the distal phalanax, which are the tips of the fingers. For this reason it is used in any activity which requires letting go of an object. Along with the extensor pollicis brevis the muscle is also used in extension of the wrist. It also helps in wrist adduction.

There are several other extensor muscles located in the wrist and forearm. For example, the extensor carpi radialis muscles and extensor carpi ulnaris are all used to control movements of the wrist and hand. Together with the extensor pollicis longus, these muscles make a variety of movements possible and help to provide the stability and function needed for small and accurate actions.

The extensor pollicis longus tendon is prone to problems because it is so regularly used. Tendinitis of the extensor pollicis longus is a relatively common and painful condition. As with all types of tendinitis, the initial stages of recovery are usually aided by resting and icing the affected area. Often the problem is caused by overuse and hence avoiding the action which caused the tendon to become inflamed is essential for a full recovery. More serious occurrences of extensor pollicis longus tendinitis may require additional treatment.


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Post 3

@SkyWhisperer - I don’t recommend splints. They will immobilize your hands and that is not a condition you want. I suppose wearing them for a few hours might be okay but wearing them overnight is not, in my opinion.

It’s interesting that the article mentions the triangle shape of the extensor pollicis longus muscle at the base of the thumb between the tendon muscles. Some time ago I saw an invention online that claimed to cure people of carpal tunnel syndrome.

It was a soft brace for the wrist, but it claimed to shape the muscles at the base of the wrist into a triangular shape, effectively reshaping your muscles in such a way that the carpal tunnel naturally opened up without the need for surgery.

I would be willing to try something like that, because it appears to cooperate with nature, rather than working against it as a splint would.

Post 2

@Charred - I experienced carpal tunnel and tendinitis too. I went to an orthopedic doctor and he gave me some exercises to perform.

These were wrist and tendon extensor exercises. For the wrist he had me grab the wrist at the base of the palm, and lift the wrist up and down at a ninety degree angle. I did this for both wrists.

For the arms he told me to do what’s called a transverse massage which is at the elbow region and it basically strengthens the tendons. He gave me back exercises to do as well.

They were very helpful in relieving the condition. I tried some splints but gave those up after awhile because I found the exercises to be much more useful.

Post 1

I developed tendinitis years ago from poor computer posture, like slouching and extending my forearms to reach the keyboard instead of keeping them level, as good ergonomics would dictate.

Symptoms included wrist pain, and hands slightly swollen at the extensor pollicus longus region, which the article describes as the region right beneath the thumb on the radial side where the forearm meets the hands.

This is also the region near where you have your carpal tunnel and I think I experienced a bit of that too. It was a difficult condition to live with for quite some time, and I tried ice packs on the affected region like the article talks about.

That helpsed, but of course when I got back to work the pain returned. The only near permanent solution was to completely change my posture, use wrist rests and take plenty of breaks.

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