Wrist extensor tendons !
The wrist extensor tendons run across the back of the wrist; they hold the wrist back so the fingers can grip strongly.
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What it is
The tendons that lift the wrist, on the back of the wrist at each side.
What it does
Hold the wrist back so the fingers can grip strongly.
Key facts
- Attaches
- ECRL and ECRB in the 2nd dorsal compartment to the bases of the 2nd and 3rd metacarpals; ECU in the 6th compartment, in the groove of the ulna, to the base of the 5th metacarpal
- Function
- Extend the wrist and steady it for grip; the ECU also steadies the ulnar side; intersection syndrome where the thumb tendons cross the radial extensors
- Tight in
- Wrist flexion with the elbow straight
Relations
- Course
- ECRL and ECRB run down the radial side of the forearm under the APL and EPB, through the 2nd compartment, and are crossed by the EPL; the ECU runs along the back of the ulna to the 6th compartment
- Deep
- ECRL and ECRB on the back of the distal radius, radial to Lister's tubercle; ECU in the groove beside the ulnar styloid, over the TFCC
- Superficial
- Extensor retinaculum; branches of the superficial radial nerve over ECRL and ECRB, the dorsal branch of the ulnar nerve over ECU
- Lateral
- Brachioradialis tendon and the 1st compartment (APL and EPB), radial to ECRL
- Medial
- Flexor carpi ulnaris, round the ulnar border from the ECU, the most ulnar tendon on the back of the wrist
How to find it
Making a tight fist with the wrist extended, ECRL and ECRB are felt on the back of the wrist just radial to Lister's tubercle, running to the bases of the 2nd and 3rd metacarpals; the ECU is felt in the groove next to the ulnar head, best with the wrist tilted ulnarly.
Examination
- ECU synergy test: with the forearm supinated, resisted radial movement of the thumb makes the ECU contract; pain along it suggests ECU tendinitis rather than a problem inside the joint
- Snapping of the ECU when the forearm turns from pronation to supination with the wrist tilted ulnarly suggests subluxation
- Resisted wrist extension: pain locates tendinopathy; weakness of all three with wrist drop points to the radial nerve above the elbow
On imaging
Dynamic ultrasound with forearm rotation shows ECU subluxation out of its groove; MRI shows tendinosis, split tears of the ECU and subsheath injury. X-rays show a carpal boss at the 2nd and 3rd carpometacarpal joints.
Clinical notes
- ECU subsheath tears happen in racket and club sports with forced supination and ulnar deviation
- Carpal boss: a bony bump at the base of the 2nd and 3rd metacarpals near the ECRL and ECRB insertions, sometimes with a bursa or ganglion
- Active wrist extension (ECRL, ECRB) powers tenodesis grasp in C6 tetraplegia
Anatomical variants
- Extra radial wrist extensor bellies or slips, and doubled tendons or cross-slips between ECRL and ECRB, are common
Memory aid
Tendons per dorsal compartment, from radial to ulnar: 2-2-1-2-1-1 (APL/EPB, ECRL/ECRB, EPL, ED/EI, EDM, ECU).
Test yourself
Think of the answer, then tap the question to see it.
Where do the wrist extensor tendons insert?
ECRL and ECRB (2nd compartment) on the bases of the 2nd and 3rd metacarpals; ECU (6th compartment) on the base of the 5th.
Which wrist extensor tendon is the purest wrist extensor?
ECRB, which inserts nearest the centre of the wrist; ECRL also tilts radially and ECU ulnarly.
Why does the wrist drift radially in posterior interosseous nerve palsy?
ECRL, supplied above the elbow, still works while the ECU does not.
What holds the ECU tendon in its groove, and what happens when it tears?
A subsheath that is part of the TFCC; a tear lets the ECU snap out of the groove in supination.
Educational information, not medical advice. For any symptom, see a health professional.
Its names
- Official Latin (TA2)
- tendines musculorum extensorum carpi TA2 2497
- Official Spanish (DeCS)
- Tendones de los músculos extensores del carpo
- English (TA2)
- Wrist extensor tendons
Related
Sources: Terminologia Anatomica (TA2); Anatomy, Shoulder and Upper Limb, Wrist Extensor Muscles.
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Representative model, for educational purposes only.
