Why does my knee pop when I straighten it?

I hate to tell you but you really needed to see a better OS doc.... there is no way that he could tell you that if you had your surgery when you where 15 that you would need a knee replacement at 30! The meniscus does not normally heal well on its own as there is very little blood supply going to that area of the knee.If your knee is still popping then the tear never healed and it might be getting worse. Please go find a good OS and get that issue fixed.