I've had very loud cracking in my knees for the past 15 years or so (I'm 25). My other joints crack and pop when I move but they aren't so dramatic. I've had a number of people ask if I've had a botched surgery or an injury to my meniscus, and most people get a little freaked out by it at first. I've had it checked out and the cartilage in my knees is a little thinner than normal but otherwise nothing is really wrong with them.
I do, most of my joints crack. Just the other day I was showing my mom how my neck cracks sometimes. My wrists do crack as well, the first to notice and even tell me was my boyfriend. He thought it was so odd and grossed him out, lol. My knees crack as well, so do my fingers. I think it's worse during the winter, no idea what could be causing it to be honest, but I do know it's been with me for a while.
I have crackling in my knees sometimes. I also have crackling in my shoulder area when I'm working out or lifting weights. It can get a little annoying when this happens, but I try to push through it in order to finish my workouts.
Now that I think of it... a lot of my joints make crackling sounds, if i move or turn the wrong way, it really is stressful dealing with all this at times, but I learned to deal with it, as I have been dealing with theses problems for a few years now.