Okay, basically, I fell while running at a full speed and landed on my knee back in 2009 and it got hurt. Then, it got better.
In 2012 I fell down stairs and landed on the same knee. It was sprained for a long time.
I joined the track team at my school this year and then my knee cap starting rubbing against some other bone and making a grinding noise?
Then today at lunch I moved my leg in to get into my seat and it made this really loud cracking noise and my friend freaked out and I can't put any weight on it without almost crying.