The 23-year-old midfielder, who sustained the injury in the recent home win over Millwall, consulted a specialist on Friday and was told he had not damaged his cruciate ligament.
Manager Simon Grayson told the club's official website: "We're waiting on a few things. The severity isn't as major as it could have been, which is positive news for us and Jonny. It's not his cruciate and he won't need surgery.
"He won't be playing for the foreseeable, but he'll be working hard with the physios in the coming weeks and over Christmas and we'll see where we are.
"I'm not putting any time scale on it, but the good thing is that he doesn't need surgery."
Source: FOOTYMAD
