The 36-year-old missed Tuesday night's 0-0 draw with Manchester United and has now been ruled out of Saturday's trip to Blackpool.
Alan Pardew: "Harps isn't right and we will have to review him over the next couple of weeks.
"He's not necessarily out for the season, but it could be that he needs a small operation just to sort his little problem out.
"It's not a major problem, but we will have a look at that and weigh that up over the next couple of weeks."