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What Is the Palmaris Longus?

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  • Written By: Alex Paul
  • Edited By: Jacob Harkins
  • Last Modified Date: 01 September 2014
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The palmaris longus is a small muscle located in the wrist, although it is not found in around 14 percent of humans as there is some muscle variation with regards to ethnicity. Even though the muscle is associated with flexing the wrist there aren’t thought to be any negative side effects to not having a palmaris longus. The muscle is located between the flexor carpi ulnaris and flexor carpi radialis. As well as flexing the wrist, the muscle is also helps to tense certain muscles.

The origin of the palmaris longus is on the humerus. It originates from the common flexor tendon. The insertion of the muscle is at the palmar aponeurosis and finishes with a thin and flat tendon. Innervation of the muscle is via the median nerve.

Aside from the fact that the muscle is not present in some humans there is also some variation in how the muscle is presented. For example, some people may have a muscle that is tendon-like above and more muscular below. Some people may have a variation where the muscle is in the center while the tendon is found above and below. It is thought that none of the variations have any effect on grip strength.

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One of the benefits of the palmaris longus being relatively unimportant is that it can be used for tendon grafts. A common wrist injury involves one of the tendons becoming ruptured. When this happens, the palmaris longus can sometimes be used to graft the tendon back together. The palmaris longus is also commonly used for this purpose due to its shape and size.

If the muscle and tendon are not present in a person who requires a tendon graft in the wrist then the tissue has to be taken from elsewhere in the body. If this is not possible then a tendon from a separate body must be used although this can cause problems due to a foreign substance being introduced into the body.

For example, in some animals the tendon is used to expose claws. It’s usually straightforward to discover whether a particular person has a palmaris longus muscle by flexing the wrist while pressing down on the base of the outer two fingers. If the muscle and tendon is present then it will be immediately visible through the skin. Although the muscle is not essential for humans, it is much more important for other animals.

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Discuss this Article

anon949270
Post 4

I tore my mcl. This tendon is used to graph it. Is there anything that I may not be able to do without it? If so please respond.

allenJo
Post 3

@SkyWhisperer - I hate to shoot down your theory, but it’s not borne out by the article. It’s clearly stated that there is no real use for the muscle.

So if there’s not much practical use, why would nature factor it in for the survival of a particular race? The impression I get from the article is that we can all live without this muscle and still go on our merry way.

If this is indeed the case, variations within the species should have no effect either way in my opinion. Although I would have to admit that it’s still curious why some people have it and some people don’t.

SkyWhisperer
Post 2

@miriam98 - I’d be interested to know just who had this muscle and who didn’t. What races or ethnicities have the Palmaris longus muscle? If so, why? The same goes for those races that don’t have it.

My guess is that we are seeing here an example of natural selection at work. Perhaps some races live in regions of the world where such a muscle is not needed. The Palmaris longus function is deemed unimportant for the survival of the species and so that race develops without that muscle.

I’m not a scientist, but that’s my best shot at a theory.

miriam98
Post 1

This is the first time I’ve ever heard of a “spare muscle” so to speak, one that some people have and some people don’t. Nature is very creative here.

While I still don’t get the relative importance (or unimportance) of this muscle, I wonder if it can be used to cure or treat carpal tunnel syndrome or tendonitis.

Perhaps a Palmaris longus tendon graft can be used for muscular repair so that you can regain full use of your wrists or elbows which may have been injured due to repetitive stress or some sport.

Perhaps it’s already been done, I don’t know, but most stories I hear about carpal tunnel surgery focus on widening the existing muscle pathway, not attempting to rebuild tissues.

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