Petrov sustained the injury while on international duty.
“Martin went to see a specialist on Monday and will fly out to see the guy that did his anterior cruciate ligament to have it re-checked,” City boss Mark Hughes said.
“The news is that it’s not his ACL this time, he’s got a tear in his meniscus that will need to be repaired.
“Although it’s good news about the ACL it’s still a bad injury and he will probably be out for three or four months.”
