I can speak to this to some degree. I'm 31 years old. When I was 13 I tore the cartilage in my right knee. The chances that it's somehow in corelation to any joint cracking is pretty non existent.
Generally torn cartilage is from hyperextension of the knee. Meaning your knee goes back further than it's supposed to, and most situations like that are sports related. When I tore mine I was playing basketball, I went up for a rebound, planted wrong when I came down and my knee went the wrong direction.. I heard a snap and felt immediate pain.
The doctors originally drained my knee (which is still one of the most painful things I have ever had done in my life) and put me in a brace. I wore the brace for sometime in hopes that it would heal normally. After getting out of the brace, there was too much scar tissue and my knee would pop out of place, so I had to have arthroscopic surgery.
In all honesty, it wasn't that bad. It's been 18 years and I haven't had a whole lot of trouble out of that knee. Sure, I have some.. but nothing major. It may get worse, but had I not had the surgery, I can only imagine how bad it would be.