I’m not sure if you guys are new to this sport, and if this ESPN deal is bringing in new fans but it’s to be expected. So I’ll give a quick backstory.
So first MMA is a sport and a philosophy, and you have multiple different organizations that sign competitors to fight. The UFC was formed in the US in 1993. It’s original matches were tournament style, and marketed as style vs style, with no holds barred, no time limits, no weight classes and essentially only eye gouging and biting were illegal. Groin shots, knees to the head of a downed opponent, soccer kicks, head butts, stomps etc were all legal back then. However in the very first match of the very first UFC Karateka Gordeau soccer kicked Sumo wrestler Tuli in the head while he was down, knocking out a few of his teeth and leaving two of the teeth stuck in the Karate masters foot. The rumor is that one of the teeth flew into the stands and landed in front of potential sponsors scouting the UFC, and were so disgusted they got up and left. Not a good way to market your sport. Not only did they lose sponsors but posed a serious infection risk to the fighter, who just wrapped his foot and continued fighting the rest of the night.
Then came UFC 12 in New York. New York politicians saw MMA and depicted it as human cockfighting, and a blood sport. They said then that the only way the UFC would be held in New York is to implement shin guards, headgear, no fighting on the ground and gloves. This completely juxtaposes the MMA theory and principles so overnight the UFC moved the event to Dothan Alabama. As you could imagine the UFC lost tons of money from the overnight move plus other states followed New York and banned mma. This is known as the dark ages of the UFC. So given a little background info you can kinda start to understand why the present day rules are the way they are. To clean up and make mma more marketable so to speak.
But to answer your question you can knee people in the head. Just can’t knee or kick what’s considered a downed opponent in the head. But you can clinch while standing and grab the back of someone’s head and knee them in the face. A good example of how devastating this is is from another mma organization Bellator, where a guys skull got partially caved in. I’ll find pictures if you want. But yeah it’s not surprising why some moves are banned in the US. However if you wanna watch people get knee, soccer kicked and stomped while down on the ground, watch some PRIDE FC highlights on YouTube. Brutal stuff. Japan didn’t give a fukk lmao