I'm 15 and I've notcied that when I eat my jaw sometimes cracks into place, when I do something with my shoulder that crakcs, and sometimes just when I extend my leg my knee cracks as well. Sometimes it even happens to my ankles. My shoulder is apparantly (according to a doctor) double jointed so that shouldn't be too bad. But at this age is it good for joints to crack like that? Is it just caused by growing bones and development?