The 19-year-old Motherwell playmaker, who tallied an impressive 15 goals during last season’s Scottish Premiership campaign, is likely to be out for an extended period as he goes under the knife in the coming weeks.
He had been linked with a move to Hillsborough, with Norwich also understood to be interested in the midfielder, before a £3.25m deal was struck up with the Scottish champions last week.
It news bring a sorry end to a protracted transfer saga that had previously seen Celtic publicly end their interest in the player, releasing a statement on Twitter lambasting the actions of Turnbull’s agent after an offer from Norwich was reportedly accepted.
A statement released by Motherwell said: "We will give David all the support he needs during this process," read a statement from the Fir Park club.
"We wish him the best with his procedure and rehabilitation, and look forward to watching him play in claret and amber again in the near future."