I'm 14 Years Old And I Am A Runner. I

I'm 14 years old and I am a runner. I run about 27 miles a week and my knees pop when I bend them. It was just my left knee and the popping was quite. However it is much louder now Andy other knee has also started to pop every time I bend them. They don't hurt when they pop unless I am putting a lot of weight on the bar while squating. Why is this, is it bad, and is there anything I can do to make it stop popping? Thank you