Abductor pollicis longus muscle

Last revised by Daniel J Bell on 16 Jan 2021

The abductor pollicis longus (APL) muscle is found in the deep layer of the posterior compartment of the forearm. As it descends, it becomes superficial and passes under the extensor retinaculum and through the 1st extensor compartment of the wrist before attaching distally. It is one of the extrinsic muscles of the hand.


Variant anatomy

  • presence of multiple slips instead of a single APL tendon 4
  •  a vertical septum splitting the 1st extensor compartment into two distinct subcompartments (i.e. APL lies in its own tunnel) 4

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