have you grown any in height? it may not be the cartlidge but that your tendons and such aren't growing as fast as your bones causing "growing pains".. either way, best to get checked out by a doctor.
are you an athlete? Do you run a lot? My husband had what sounds like what you're experiencing. I know my spelling here will be horrid, but it was called an maniscus tear? I know that's prob. not how you spell it. But it was due to the wear and tear from him jogging. He had to have surgery. When it was healed it was good as new. Now the other is bothering him. lol
The surgery itself didn't really put him down. He just iced for 3 days. He could walk around. But it was um... 4 or 5 months before he started running again.