Both of my knees "creak" and crackle and have for years. Back in the day, when I worked out at a gym instead of in my garage, I was squatting, and the person spotting me said, "man, your belt is creaking a lot." To which I said, "what belt?" Knees...and that was in 1988. All of which is to say, they creak, but they work. I have always assumed it was something degenerative, but so far, so good.