the problem was not the the knee was from the bottom but that it was to the back of the head, this is potentially devastating and can cause permanent damage. This and the fact that frank was pushing his knees off of the fence.
I say this as objectively as I can because I train BJJ under one of Renzo's students.
Anderson Silva (MW)
Randy Couture (HW)
Quinton "Rampage" Jackson (LHW)
Roger Huerta (LW)
Karo Parisyan (WW)