Tendon of abductor pollicis longus

The tendon of abductor pollicis longus muscle originates from its muscle belly in the extensor region of the forearm. It then courses distally, passing through the first dorsal extensor compartment of the wrist, deep to the extensor retinaculum, which serves to hold the tendon in place and prevent bowstringing during wrist movement. Typically, the tendon of abductor pollicis longus lies lateral to the extensor pollicis brevis tendon. Together, these tendons form the lateral border of the anatomical snuff box on the dorsum of the wrist.

The primary insertion of the abductor pollicis longus tendon is at the base of the first metacarpal bone. However, accessory slips may also insert into the trapezium, the abductor pollicis brevis, or even the capsule of the first carpometacarpal joint.