Ok so I am an avid skateboarder. and all of the sudden my right knee really hurts when i am stepping up objects like stairs etc... Also my knee is always buckling or giving out an i am falling all over the place. and ontop of that my right angle is sprained, and has very limited mobility. I cannot turn it on its side, or roll it sideways. so my right leg is screwed. but back to the knee. its pretty swollen and it seems like it has fluid in it. my knee cap is especially loose too. im 14 and feel like im 80. any one ever deal with this at a younger age. All i can find is stuff about old people with arthritis in the knee. pleas help. im going to the doctor soon, but i want to get some additional info about it. thanks in advance