In 2364, the Phoenix was sent on a punitive mission to wipe out a Cardassian colony on Setlik III. One of the combatants stabbed Earthfleet officer Miles O'Brien in the right knee, a wound that left a permanent mark. Helot Jadzia Dax learned of the injury because she served as medic on the Phoenix at the same time. She passed the knowledge on to Ezri Dax. (ST - Myriad Universes novella: Seeds of Dissent)