Tendon of extensor carpi radialis brevis

The tendon of extensor carpi radialis brevis is visible in the mid-forearm. It runs close to the tendon of the extensor carpi radialis longus. As they approach the wrist, these two tendons pass together underneath the tendons of three deeper muscles of the thumb: first, the abductor pollicis longus and extensor pollicis brevis, and then the extensor pollicis longus. Finally, the extensor carpi radialis longus tendon continues its path by passing beneath the extensor retinaculum as it approaches its insertion point on the hand.

Insertion of the tendon

The tendon of extensor carpi radialis brevis primarily inserts onto the dorsal (back) aspect of the base of the third metacarpal bone. Occasionally, small slips of the tendon may also attach to the base of the second metacarpal bone.

Functional significance of the tendon

Through its tendon, the extensor carpi radialis muscle is instrumental in extending and abducting (moving towards the thumb side) the wrist. Furthermore, due to the strategic insertion of this tendon, it contributes significantly to dynamic wrist stabilization during activities like gripping and repetitive hand movements.