Why did i get arthritis on my good strong leg just from bending my knees ?

I'm 26 male. on january i was video taping and in order to lower a bit, i bend my knees a bit and stayed in that position for like 10 seconds.. when i came back up i knew something had torn or something. very very unfair, cause it was such a simple thing i did. Plus that leg is my strongest, the other leg is slightly smaller and weaker but the injured one has strong muscles. So i'm thinking it was the imbablance of leg length and imbablance in muscle strength that somehow caused this. Ok, Now i'ts June, had this on January and although it's better i have bone pain sometimes alot that i cant' even walk. I know it's probably mor elike bone related( that is why im calling it arthritis), i'm not sure what it is though. I've heard of osteoarthritis happening to athletes even when young..so is it this? and man, i have to live the rest of my life without being able to walk well? I went to doc, but he was an ignorant doc that just wanted money. anyways, what can i do for this?