Silly!

You know, my oldest stepdaughter was the same way - she'd jump to the worst possible conclusion over her aches and pains when she was a teenager!

Actually - now that I think of it - I did it too! Every month I was dying. I remember being convinced I had leukemia.

I'll bet you $100 that it's not bone cancer. You're much too young to be a likely candidate for that, for one thing. For another thing, the pain with bone cancer is absolutely excruciating, once it occurs. But usually you start breaking bones really easily first, before you even begin having any pain with it.

There are hundreds of things which could cause knee pain, all of them much more likely than cancer! So take a deeeeeep breath and cuddle up with a kitty and relax! If it hurts badly enough that it keeps you from using it properly, or if it doesn't start improving soon, go to the Dr.