Hi purpleape! and Welcome to HW/CP! Right now I have to pick up my boys from the ball field, so I can't respond with much atm - but I wanted to take a sec to welcome you (tho sorry that pain is what caused you to find us!). I had terrible knee pain/issues when I was a teen. I actually had horrible 'growing pains' during my pre-teen years that affected my legs - it was AWFUL! The pain you described sounds very familiar. I injured both my knees playing basketball - dislocating one of my kneecaps.
I really have to go now, but I'll be back on later - and others will be here throughout the weekend. Some days tend to be a little slower than others, so please don't feel you're being ignored if you don't get many responses right away - you will definitely be hearing from other CPers. Hang in there!
And again - Welcome!