Fig. 1

Fig. 1. The mechanism of A1 pulley stretching. A. The relationship between bones, flexor digitorum superficialis (FDS) , flexor digitorum profundus (FDP) , and A1 pulley. B. The combined force of the flexor tendon traction force and the counteracting force pulls the A1 pulley to the palmar aspect and enlarges the A1 pulley lumen.