I have no idea how I did it, I have not fallen on it, twisted it or anything. I chaperoned a field trip to the zoo for my 2nd son's class and by the end of the day my right knee was killing me, it was so excruciating that every step I took I felt like I was going to puke, I have a high tolerance for pain, but this was bad. I got home and realized my knee had swollen considerably, at this point I had to be to work within an hour and of course I had machines down all night and ended up being on the production floor all night fixing shit, not good for my knee. This morning I bought a knee brace and it seems to be helping, it keeps my leg stiff when I walk so now I'm just walking slow but it doesn't hurt nearly as bad. I hoping the machines run well tonight so I can stay in my office and stay off of it. If it doesn't get better in a few days I'll go to see the doctor.