I don't buy the PED/HGH arguement. I tore mine, and haven't done any of those. I think what is happen is we are having the first generations of kids come through that have extensively lifted weights while kids. Their muscular systems have outgrown their skeletal systems and consequently they are ripping their joints apart.
I have a friend that this happened to. He was identified as having the potential to be of olympic caliber with regards to his endurance sport at a young age. Hit weights, not seriously but more so than the average kid before puberty. Problem is, he never grew that much, was no more than 5'5". HIs club coach told his college coach "no weights", the college coach didn't listen, and he started getting arthritic joints & had to quit the sport.
This is essentially what Michael Phelps coach, Bowmann, avoided. Phelps didn't hit weights until before the Beijing olympics, for the exact fear with which I have described above. Now that he has finished growing, and knows what his frame can handle, he can afford to put weight on without these fears.
For these reasons, I think the propensity for ACL injuries in football & basketball players in the last 10 years is the fact that we have overwhelmed our evolutionary skeletal capacity.