my legs always click, dont even realise most of the time that they need to click, if i bend down they click so loudly, everyone always makes a comment about it! i sometimes have to click them myself like if im sitting down and it feels like they need to be clicked then i just swing them backwards and forwards til they click. my knees lock as well a lot, especially my right one, and its so painful to unlock them i hate doing it. one time i couldnt actually unlock it and i had to go into hospital and they couldnt do it either, even after an operation on it! my fingers and back sometimes click too but not that often
you could go and see your doctor if youre worrided about it, but from my experience theres not really anything they can do