What could be wrong with my knee...?

I'm a catcher for my softball team and sometimes while I'm catching, when I get up fast, I'll feel a pop in my knee and then it hurts around my knee cap and sometimes the back of my knee. I'll finish the game, then it will hurt for a couple of days, but then be fine. This happens almost everytime I catch. I've stopped catching for the season now and have had a couple weeks off, and now I'm on to cross country. It doesn't hurt often, but once in awhile just the back of my knee will start hurting again. Does anyone have any idea of what this could be? Thank you!!!What could be wrong with my knee...?
go see a sports medicine doctor before you cause serious injury. I used to be able to train for 4 straight hours. I was doing endurance training. I ended up pulling a muscle in my leg from either kicking or playing tennis (don't know at what point it happened). I thought it was just fatigue and kept on going for months, before it finally progressed to the point where running for prolonged periods causes intense pain in my leg.



long story short. don't be stupid like me and try to fight through it. be smart and see a doctor.What could be wrong with my knee...?
Our family has fibermaliga, and yes, i know i didn't spell that right, and it runs in family's. It might be that, or muscle pain, i am 11, and that happens every once and a while at dance. hope you feel better soon!