The Blues striker has been troubled by the injury for most of the season which has restricted him to making just six first team starts during this campaign.
Garry's going to be out for a while," Blues boss Alex McLeish has said.
"The surgeon said he didn't know how he had been managing to play through it.
"We knew there was something wrong with him mobility wise but he has always given everything on the training ground and on the pitch whilst playing with some pain."