ONE Championship does not abide by the Unified Rules of MMA adopted by the US athletic commissions.
They have their own sets of rules that they call the Global Mixed Martial Arts Rule Set.
Knees to a downed opponent are legal in ONE Championship.
What about the safety of the fighters? Are knees to a downed opponent risky to fighters’ safety?
Obviously they are! But the sport of MMA is not a tickling contest, it is a sport designed to inflict damage and receive it.
Knees to a downed opponent aren’t more dangerous than elbows to a downed opponent, they all inflict a lot of damage and have the potential to knock the fighter out.
On the other hand, many voices in the MMA community have risen against this rule and demanded it to change.
Here is a tweet by Aljamain Sterling speaking up against this rule
This is why knees to downed opponents are vicious and ILLEGAL in MMA in the UFC! If this was the USA that knee is not allowed and Mighty Mouse can get up in a more safe and protective manner.— Aljamain Sterling (@funkmasterMMA) April 8, 2021
I hope Mighty Mouse is ok, but this is why I disagree with those rules. #ONEonTNT1
Are there fighters who are in favor of knees to a downed opponent?
Ironically, former UFC champion Demetrious Johnson, who once got knocked out by the same technique in ONE Championship, has expressed his support for the legalization of knees to a grounded opponent.
Here is a tweet by Demetrious Johnson where he supports the legalization of the technique
Heres the thing you cant stall the fight by sitting on your knees. Knees to a grounded opponent should be allowed!— Demetrious Johnson (@MightyMouse) March 7, 2021
Why did ONE Championship allow knees to a downed opponent?
The reason why ONE Championship allowed knees to a downed opponent is that they keep the fight moving and exciting.
Also, they prevent fighters from just staying in a passive position and letting time pass, like what often happens in the UFC.
For example, many fighters in the UFC just turtle down and take their time to rest.
This wouldn’t happen in ONE Championship, simply because the fighter who is turtling down will risk a knee to the head from their opponent and therefore get knocked out.
Here is a video showing a highlight reel of the best knees to a downed opponent in ONE Championship