I am a 19 year old male and I'm not sure if this is normal or not.

From the standing position, when I squat down all the way and my knees bend til the resting point, they crack a little (I can feel it and it's audible). When I begin to stand up and pressure is put on my knees to stand, they make a crackling sound, almost like the noise made by crumpling up a piece of paper. Something similar happens when I slowly bring my arm forward and up and back (almost in a circular motion).

It sounds as if my bones are very brittle or my joints aren't lubricated enough or something, though I'm pretty sure I get a healthy amount of fat a day. At the top of my head, I can only think of two possible reasons that may have been the gradual cause of this, assuming this isn't normal:

1) When I was around 11-12 years old, I took these "milk" pills that were chewable that were supposedly help me to grow taller. I'm not sure if I'm allowed to say the name of the brand here.

2) I've been doing intense plyometrics for the past 5 years, training to increase my strength by doing rapid movement exercises. Most of the work I do doesn't involve weight, but primarily bodyweight exercises so I don't really use heavy stuff. But the thing is, I haven't done much stretching before/after my workouts at all.

So this is a concern for me, because I don't want to have early arthritis or something because the bones at my joints are weak or something. Will fish oil or glutamine help my condition or is it not normal at all for my bones/joints to make such sounds?