It leaves Blues short of attacking options as back-up to the current front two of Cameron Jerome and Christian Benitez.
Birmingham manager Alex McLeish confirmed: "We have received some disappointing news about Garry. He is likely to need an operation on his hip.
"It could keep him out for several months and leaves our striking options light."
City's on-loan midfielder Teemu Tainio is also facing a spell out of action with a knee problem which could require surgery.
The Sunderland player has made only five starts for Blues.
McLeish admitted: "Teemu is another player who may need surgery as his knee problem has flared up again.
"We knew he had a bit of a problematic knee before he came here but we were hoping he would be able to stand up to it.
"He is going to be out for the immediate future."
Wolves 11/8, Birmingham 2/1, Draw 9/4