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You do not say how old you are. Popping noise when flexing the knee under load could indicate a meniscal tear, The meniscus is the tissue that is the shock absorber between the leg bone (femur) and the shin bone (tibia) in the knee. It has the consistency of hard chewing gum and takes a good deal of the load off the knee joint. When there is a tear, there can be a popping sound when it catches. A common tear is called a bucket tear.

The crackling sound could be a bone on bone event. Think--your shock absorber has been torn or misplaced and your leg bone is hitting your shin bone with no protection. Hope this helps. Good luck.

A method to prevent this from happening would be to wear special knee pads to prevent injuries from occurring. It also provides support which sounds like you could use while in sports mode. Try this after seeing the doctor and see if it will help you as I see that you may have this problem for the rest of your life. Get the good sports one, not the cheapo. It makes a difference.

U could have torn your meniscus thats wht i noticed and i gt an mri and they said i had torn my meniscus i had surgery to repair it on monday.

air bubbles are poppoing. breathe less.