The 28-year-old midfielder has looked short of his best form during the opening weeks of the Championship season, but Leeds have kept news of his problem quiet since the Palace trip.
Derry is expected to go under the knife in the coming days, although boss Kevin Blackwell admitted the club could still opt to delay surgery until the second international interlude at the end of next month.
Blackwell said in the YEP: "Shaun will see a top specialist in Germany and if he needs surgery now then that's the road we'll take. But if the surgeon decides that Shaun is able to carry the problem for another six weeks then we'll wait until the next international break before reassessing things."