What do you think of this fact?
Try this: press the tip of your thumb against the tip of your pinky and bend your wrist slightly toward you. See a thin cord popping up in the middle of your wrist? Congrats, you have a palmaris longus. No cord? Then you might be missing a whole muscle.
The muscle some people just don’t get
The palmaris longus is a slim muscle in your forearm. It starts at the inner bump of your elbow and ends in a long tendon that fans out into the tough tissue of your palm. According to StatPearls, depending on the population studied, somewhere between 2.5 and 26 percent of people are born without it. Physiopedia even says almost 30 percent could be lacking it in one or both forearms.
And it gets stranger. Missing it on both sides is more common than missing it on just one, and studies report it is absent more often in women. The thumb-to-pinky trick above is a real clinical check, known as the Schaeffer test.
Does it even do anything?
A little. It helps bend your wrist and keeps the tissue in your palm under tension, which seems to steady the skin of your palm. But StatPearls calls its actual contribution to bending the wrist “likely minimal”. The bigger surprise: people who don’t have it show no weaker grip or pinch strength. Your body simply doesn’t miss it.
Anatomists have a fitting label for this kind of muscle. Physiopedia describes the palmaris longus as “phylogenetically retrogressive”: a short muscle belly attached to a long tendon. Put simply: a muscle that seems to be in retreat over the course of evolution.
Surgeons value this tendon. Because it’s so easy to spare, they harvest it as a graft to repair other tendons in the hand and fingers, or to treat severe carpal tunnel syndrome.
So go ahead and test both wrists. Two cords, one cord or none at all: every result is normal. It’s just your forearm quietly showing you which version of the human blueprint you got.