I am 15 years old and when I bend my knees they often make a clicking/cracking sound, they also creak but rarely and only ever very slightly. It does not happen when I only bend them partialy, e.g. walking up stairs etc... but it happens almost every time when I bend them much more than that. There is no pain and it is not seriously afecting my life at all but it is rather annoying and I would like to know if it is something I should be concerned about and possibly if there is a way to eliminate the problem.