The two muscles affected are the extensor pollicis brevis (EPB) and abductor pollicis longus (APL). These muscles lift the thumb and move it out to the side. De Quervain's tenosynovitis occurs ...

Scar tissue develops within the flexor sheath, decreasing the space available for the tendons. Late direct repair is most commonly performed in the thumb ... the flexor pollicis longus (FPL ...