Rangers have confirmed Lee McCulloch is to undergo surgery next week to determine the full extent of his knee injury.
The 32-year-old had been playing through the pain barrier with a cyst in his knee since pre-season but was forced off during last Wednesday's win over Hearts and missed the Scottish Cup draw with Celtic last Sunday.
It has been suggested the problem could force the midfielder to miss the rest of the season.
However, Rangers insist they are still waiting to find out how long McCulloch will be sidelined for.
A statement on the club's official website read: "McCulloch visited a specialist yesterday when it was confirmed that he would require an operation to clear up the cartilage problem.
"It is planned that this will take place next week and it will be when the procedure is under way that the surgeon will know the full extent of it.
"Rangers are bracing themselves for Lee missing the rest of the campaign but there is some hope that this might not be the case."