Incredible that he continued playing football but I hope Cain was misquoted. If it is a full-thickness ACL tear and the person's quad muscles are well-developed they serve to lock the knee down to increase stability. It still doesn't "feel right" but you can run and such on it fairly well but performance should be weakened. The first few days are terrible. I'm more shocked that he played on the torn meniscus because of the potential for further damage. He's a warrior for sure.
For those that don't know me, I'm not entirely full of it. I work in PT and had a full thickness tear of my ACL on Labor Day 2010, MRI the week before Thanksgiving and surgery in January.
Thanks for the link. I'm going to talk to him about this Friday night. I'm interested to hear more