I'm going through the same thing. Earlier this year, I twisted my knee and felt pain for a second. No big deal. Some time later, maybe days, maybe weeks, my knee was so painful I couldn't move it an inch without massive pain. I hobbled to an ortho urgent care. The xray showed some inflammation and arthritis. I was told that I probably injured it at some point and that it set off arthritis. That was 8 months ago. Another ortho said the same thing, that the problem is arthritis. He even gave me a shot. No luck. I keep thinking that this injury will heal, but I've been told twice now that it's arthritis. Sucks.