My ankles and knees have been cracking every since I was 12 years old when I got sick and nearly 40 pounds in two months due to throwing up everything I ate. Now I am 20, and my ankles and knees still crack with every step I take and will give out or lock up on occasion, especially during exercise. The pain has moved up to my hips and shoulders, and will leave me up all night. I have been to many doctors, who all claimed I would grow out of it, but the pain seems to only be getting worse.