Extensor carpi radialis longus
One of the muscles that cocks the wrist back — and a large part of why you can grip hard at all.
- Type
- Muscle
- Region
- Forearm
- Standard name
- m. radialis longus extensor carpi
- Origin
- Lower third of the lateral supracondylar ridge of the humerus
- Insertion
- Base of the second metacarpal
- Actions
- wrist extensionwrist radial deviation
- Verify
- TA2 2497 TA98 A04.6.02.040
What it is
A long muscle running down the thumb side of the back of the forearm, just behind brachioradialis, from the outer edge of the humerus to the base of the index finger's metacarpal.
It arises slightly above the common extensor tendon rather than from it, which distinguishes it from most of its neighbours.
What it does
Extends the wrist — cocks the hand backwards — and deviates it towards the thumb.
Its important and underappreciated job is stabilising the wrist during gripping. When the finger flexors contract to close the hand, they would also flex the wrist if nothing resisted them. The wrist extensors contract to hold the wrist steady, which is why your wrist naturally extends slightly when you grip hard, and why grip is much weaker with the wrist bent forward. Try it: squeeze your hand with the wrist cocked back, then with it bent forward.
What loads it
Gripping, which loads it isometrically in almost every pulling and carrying movement. Also resisted wrist extension.
What is commonly got wrong about it
That grip and wrist extension are unrelated. They are directly linked — you cannot grip strongly without the extensors working to hold the wrist.
That "tennis elbow" is this muscle. The finding usually points at extensor carpi radialis brevis, its shorter neighbour, whose origin sits right in the middle of the common extensor tendon.