The 24-year-old, who joined Wednesday from Chelsea in the summer, started his first game since August in yesterday's 3-0 defeat to Watford, but lasted just seven minutes.
"He's gone up for a header and as he's come down, he's twisted his knee," Owls boss Stuart Gray told BBC Radio Sheffield.
"We'll assess it and we'll probably get him scanned. It's disappointing for him, but we've just got to move on."
Defeat to top-of-the-table Watford means that Wednesday are now four games without a win and down to 11th.