Palmaris longus
The forearm muscle a large minority of people simply do not have — and nobody misses.
- Type
- Muscle
- Region
- Forearm
- Standard name
- m. palmaris longus
- Origin
- Medial epicondyle of the humerus, via the common flexor tendon
- Insertion
- Flexor retinaculum and the palmar aponeurosis
- Actions
- wrist flexion
- Verify
- TA2 2482 TA98 A04.6.02.029
What it is
A small muscle with a short belly and a long thin tendon, running down the middle of the front of the forearm to fan out into the palm.
It is absent in a substantial minority of people, on one or both sides. Reported absence rates vary widely between populations and studies, which is worth stating rather than picking a convenient figure — it differs markedly between ethnic groups.
You can check your own: touch your thumb to your little finger and flex your wrist slightly. If a tendon stands up in the middle of your wrist, you have one. If nothing appears, you do not, and this has no consequences whatsoever.
What it does
Weakly flexes the wrist and tensions the palmar aponeurosis, the sheet of connective tissue under the skin of the palm.
Its contribution to grip and wrist strength is negligible — which is why its absence is unnoticeable, and why it is a favourite donor tendon for reconstructive surgery elsewhere in the body.
What loads it
Wrist flexion, negligibly, alongside much stronger muscles.
What is commonly got wrong about it
That missing it is a defect. It is an ordinary anatomical variation with no functional cost. It is sometimes described as vestigial, which is a reasonable reading, though "vestigial" claims generally deserve more caution than they get.
That the visible tendon indicates strength or its absence weakness. Neither. Grip strength has been compared between people with and without it and no meaningful difference has been established.