I don't really know, but i suffer from clicky knees and i do worry about what they will be like when i'm older. It drives me nuts, everytime i stand up from sitting down they sound like a ratchet spanner. It's not painful as such, but just what i'd describe as 'uncomfortable'. I blame it on two things; too much football, and squatting too heavier weights in the gym during my 20's, but it's probably got a much more simple explanation than that. Like i'm getting old. (i'm 32)