Veteran referee “Big”  John McCarthy helped established the Unified Rules of Mixed Martial Arts in the early 2000s, but there’s one rule that he would change given the change.   “I would love to see it knees to the head someday, but I don’t think it’s going to happen, but I would like to see it,” McCarthy told  MMA Junkie Radio . “I think it would be a good thing for the sport.” Knees to a grounded opponent are illegal but whether they should be allowed has long been debated.  They are permitted in Asian promotions Rizin FF and ONE Championship.   “I’m going to be honest, as a fan of the sport and even as an official, I look and say knees to the head to someone that’s on the ground, not soccer kicks, it’s different, but knees to the head of somebody on the ground could be effective in the fight,” McCarthy said