Check out this video from Survivor Series, which shows CM Punk grabbing his knee in pain after he and John Cena worked together to suplex Ryback through the announcers table. It’s unknown if Punk was dealing with a knee injury prior to this spot, but he was showing signs of a bad knee after this took place.
http://www.youtube.com/watch?feature=player_detailpage&v=LCRjZkgMnxU