Oh, my. I'm so sorry. I wish you the speediest of recoveries and yes, you're very lucky you got to keep your knee, and I really do hope your knee doesn't cause you pain. My boyfriend's uncle was in a similar wreck, somebody in front of him changed lanes and then hit the brakes; he slammed into them going about 70 mph and flew over the front of their car, ~50 feet. They thought he would die overnight.
He didn't lose any limbs, technically...but in reality, he has. His legs pain him all day and all night to the point that he cannot work and can barely walk. He -should- be in a wheelchair or at least using a cane, but he's a tough military guy and refuses.
Motorcycle accidents often end up terribly grotesque and tragic. I'm very glad you're alive and I hope you do well! Best of luck to you and please keep us posted.
And some advice...don't be like the guy I talked about above...Accept help when you need it! It will help you in the long run.
Again, good luck, I command you to get better soon.
And...find those teenagers and throw them in the slammer. -_- Idiots...