Sore knees from Heel up?

Steven P

Long story short, I have had pretty sore knees for a while. Been to docs god knows how many times and they say it's just growing pains... (18 yrs old). Every time I go on I'm OK but when I come off I'm usually sore. I play fast metal. I'm not straining or anything, I'm relaxed. I play Axis A's, 80-90% tension, beater about 4-5" from head. (I have tried other settings). I have tried sitting at different angles etc but nothing. It makes me think, is it Heels UP that is the problem, since I need to lift my leg and use my muscles to keep my leg held in air whilst my ankles take over... If any of this makes sense... Would heel down do the trick? Thanks