The New York Times is reporting this may be the case. (Just now, on YES it was reported that the Yankees will not confirm this report.)
From what I can quickly tell, if surgery is required, Posada could be out for the next four to six months (post-op). So, this situation would basically wipe out his season.
While the Yankees would miss his bat behind the plate, Jorge being MIA would also be a huge loss in terms of the leadership that Posada provides the team.