abductor pollicis longus

The abductor pollicis longus (abductor pollicis longus muscle) is a long muscle located in the posterior (extensor) compartment of the forearm. It abducts the thumb at the carpometacarpal joint and also assists with radial deviation of the wrist.

The abductor pollicis longus lies in the posterior forearm, immediately below the supinator muscle and sometimes partly united with it. Its tendon passes through the first extensor compartment of the wrist alongside the extensor pollicis brevis, traveling obliquely across the wrist to insert at the base of the first metacarpal.

The abductor pollicis longus abducts and extends the thumb at the carpometacarpal joint, pulling the thumb away from the hand. It also assists with radial deviation (abduction) of the wrist. This muscle is essential for positioning the thumb for grip.

De Quervain's tenosynovitis is a common condition where the tendon sheath of the abductor pollicis longus (and extensor pollicis brevis) becomes inflamed, causing pain over the radial (thumb) side of the wrist. This is especially common in new mothers and individuals performing repetitive thumb or wrist movements.

The abductor pollicis longus is an extrinsic forearm muscle with a long tendon reaching the base of the first metacarpal, while the abductor pollicis brevis is an intrinsic hand muscle within the thenar eminence acting on the proximal phalanx of the thumb. They produce complementary abduction at different joints.