The 30-year-old Bulgarian limped out of the 2-2 draw against Fulham at the weekend and looks set to miss the clash with the Iron on Wednesday.
City boss Mark Hughes hopes the injury is not a serious one, after Petrov repaid the faith shown in him by his manager by scoring the Blues' second goal against the Cottagers at Eastlands on Sunday.
"I felt it was important for Martin to play," Hughes told the club's official website.
"He's been doing well and I didn't want to disappoint him. He was keen to get the ball and scored what should have been the winner.
"But he got a bang on the knee and was unable to finish. It's been sore for a while now. Hopefully it won't be too serious, a bang and not a twist."
City captain Kolo Toure is also a doubt for the game at the City of Manchester Stadium with a heel injury, while striker Roque Santa Cruz is suffering from tonsillitis.