if its a knocking noise when you go over bumps, it sounds like it could be your ball joints??? does it happen when you brake a bit hard a completely stop, when weight thrown on the front suspension normally makes ball joint clunk on the rebound (when suspension on the way back up). just get it checked out and get the parts your self. if it is track rod ends then your can do it yourself, it a easy job, but you have to get tracking done after (straight away).