yes Dover is correct.
How active is he how much is he eating, sounds like he just needs more calories, lack of calories /nutrition at a young age is the leading cause to stunt growth from his genetic capacity.
there are so many older powerlifters that have been squatting heavy all there life, and don't have replacements. It is very unlikely I will need to get one done. I have trained and redesigned my body to handle the heavy weights.
I hurt both my knees back in highschool pretty bad, never had surgery, after highschool i rehabed them with squats, then heavy squats, knees are pain free now.
shrug.