I am 20. Not to worried. Right now i know my back injury is just overuse and i need to rest it. The knee injury i think i am going to have to pay attention to possible for the rest of my lifting career if it doesn't fully heal up. But i need to keep in mind i am STILL pushing it and making crazy strength gains even with the knee still in its healing process so i think if i take some time off and let my tendons and stuff catch up it would be best in the long run for me. I really don't plan on doing anything serious until the end of summer if i am healed up by then.