Will I need a cast for my knee....?!

I doubt that they would do serial casting on a teenager - it would hinder growth and development too much... Having said that, it has been done before. A normal cast - not a chance.

If the docs were to decide that serial casting was the best option moving forward, then expect the casts to start above your ankle and extend to the top of your leg. You'd start off with getting a new cast every 3-4 days, then move to one a week after 2 weeks, then probably a cast put on about 4 weeks after starting treatment that would stay on for a longer period - maybe 2 weeks but as long as 8 weeks.

But like I said, I doubt it. Serial casting tends to be a muscle development treatment rather than bone disease/condition treatment. In my opinion, some sort of surgery or a knee replacement would be far more likely, and far more effective.

Good luck :)

no because putting it in a cast will make it hurt more when it comes out of the cast because you haven't been moving it so it is more stiff. trust me i know i have had JRA since i was 9

nope no cast for that sorry. you may get crutches.