That happened to me, we had a lot of LEO and military in my class, was rolling with a new guy from the guard and he tried putting a knee bar on me, which was not allowed below purple, I told him to let it go, he kept cranking, I rolled out and starting applying a collar choke on him very slowly, I told him, I own a restaurant and on my feet every day, you fuck up my knee, I will fuck you up. If you want to go Vale Tudo, we will, stay away from my knees. I let it go before he passed out and never rolled with him again.