I dropped in to BJJ the other day, and had my knee popped. I was passing guard but ended up in what looks like 50/50 guard. I was still standing and he figure foured my leg, then straightened his body to try to sweep. But in retrospect I think his legs were too close to my knee and not higher up to my hip. I felt no danger to be swept but my knee lightly popped with minor pain but no swelling. Rolled lightly for the rest of the class. I would have trouble walking afterwards and by the morning could barely put weight on it. Now, one more day after, I can hobble around and even stand on that one leg only, but it's still tight and a bit tender. A bit hard to straighten fully. I think it's a sprained LCL. Now here's the thing: we were rolling light and the guy was a purple belt smaller than me. I don't think he was going for a submission and I've had no previous knee problems. I wasn't warmed up though. It seems to me the 50/50 allows someone to put too much pressure on the knee accidentally. What do you guys think?