What Is An Illegal Knee In The UFC?

The knee strike is a perfect close-range weapon in a fight and can be transformed into a long-range missile when performed with a jump. And while knees are generally permitted in MMA, in some scenarios, they are illegal.

A knee is considered illegal in the UFC when it lands on a grounded opponent.

At first glance, this simple rule has caused some confusion and controversy in the last few years. Let’s see when knee strikes are illegal in the UFC in more detail and look at some good examples.

What Is an Illegal Knee In The UFC?

Knees are illegal in the UFC and under the Unified Rules of MMA when they land on a grounded fighter. And to quickly answer the question, a fighter is considered grounded when both his palms, fists, one knee, and/or any other part of his body are touching the floor. In this case, no kicks or knees are permitted, including up kicks.

This is the written rule, but judges often consider even one palm enough for a fighter to be grounded. Before implementing the unified rules of MMA in 2009, a fighter was grounded if ANY body part but the soles of his feet touched the ground.

This led to many fighters taking advantage of the rule and placing just one or two fingers on the ground to prevent incoming knees or kicks.

Some organizations, mainly those based in Asia like One FC and Rizin FF, allow knees and kicks to a downed opponent with the pretext that elbows and other strikes to the head are not less dangerous. This changes the ground game quite a bit, negating some stalling tactics.

Are Knees Allowed in The UFC?

Are Knees Allowed in The UFC

Knee strikes are widely used in Muay Thai, kickboxing, and MMA, as the freest combat sport. Knees are a very versatile weapon. They are perfect for use at close range and are deadly in the clinch.

 Just watch a Muay Thai expert execute with deadly precision once he acquires the advantageous position of the hands (often called the Thai plum).

The knee becomes a strike capable of covering a significant distance when it becomes a jumping knee. It is also the bane of many wrestlers who dare to shoot for a double leg takedown without any setup.

A knee to the body of a grounded opponent is a very potent strike. Many fighters use them to blast the ribs from side control or even hit the legs from the back.

But there is a serious inherent risk of hitting the head. If a fighter is seated on the side of the fence and you try to plant your knee in his solar plexus, the risk of a foul nearly doubles.

What Happens If An Illegal Knee Lands?

Unfortunately, from time to time, fighters do land an illegal strike. Although they are trained professionals, sometimes their judgment is not optimal in the heat of battle, and most of the time, these are incidental.

When an illegal knee lands, the referee stops the action and pauses the clock. The victim has 5 minutes to recover, and the offender often suffers a point deduction.

But if the strike is too severe and the fighter cannot continue, he can be awarded the win by disqualification. If the foul happens too early in the fight, the result is usually declared as a “No Contest.

There are quite a few examples of illegal knees in the UFC, but none is as stark as the one landed by Peter Yan on Aljamain Sterling at UFC 259. This is perhaps the only time a title changed hands because of a disqualification.

The champion, Petr Yan, was well in control of the fight, dominating the striking and wrestling exchanges. Still, in the fourth, he made a grave mistake and followed bad advice from his corner, landing a strong and clearly intentional knee on Sterling, who was on his knee.

While the strike was as illegal as it gets, Sterling did put on a spectacular performance (according to this humble writer and the overwhelming majority of MMA fans) and refused to continue the fight. This way, he won the bantamweight title in a fight he was losing.

Another interesting example is the all-time great Demetrious Johnson. During his reign as UFC champion, he regularly voiced an opinion on the allowance of knees to the head on the ground.

Then, when he moved to One FC, he fell victim to a left knee on the jaw while on the ground by Adriano Moraes. Despite suffering his first stoppage loss this way, Mighty Mouse continues to support the rule.


MMA is a relatively young sport, and some rules do require adjusting. Unlike boxing, where the rules are uniform globally, MMA still allows different interpretations. The knee strike is one of those gray areas. In the UFC, a knee to an opponent on the ground is illegal, while in Asian MMA organizations, it’s legal.


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