The French midfielder is struggling with the problem and even though the club is set to get a second opinion on whether or not he requires an operation, Pardew fears he may lose him for up to six weeks.
"He's seeing [someone to get] a second opinion tonight on just whether we feel an operation necessary," he told Sky Sports News.
"I think that probably will be the case and he'll miss four to six weeks.
"He's a very important player but we need to have him right. It's no good him playing at 80 per cent which he's done for the last three or four games so we have to get him right."