How can i help my growth spurt?

You cannot do anything about your growth spurts. It is a naturally part of puberty. While also, the hurting your knee cap when you run is probably due to your growth spurt and the temporary imbalance you're suffering at the moment. My boyfriend grew a foot and a half when he was your age and there's nothing to change it. You will also suffer from stretch marks (normal on guys who have growth spurts) and you can try to prevent those.