The knee is near the end of the survelance film. She pulls a drunk guy into a washroom and wants to get his pants off and he refuses. So, she pushes and hits him a couple of times and before leaving knees him in the nuts. He really groans when she does the knee. I wish it was a better angle but it's still a "real" knee to the nuts.
http://www.machovideo.com/video/Unlucky_boy_22384/