Knee Strike

Last updated: May 25, 2026

What is a knee strike?

The knee strike is one of the oldest weapons in stand-up fighting, and a defining part of Muay Thai’s art of eight limbs framework that treats the fists, elbows, knees, and shins as four pairs of striking tools. According to Wikipedia, knee strikes are native to traditional Southeast Asian and Okinawan martial arts and entered modern combat sports through Muay Thai, kickboxing, and eventually MMA.

In a fight, a knee fills a specific gap in a striker’s arsenal. Punches work at striking range, kicks at the outer edge, and the knee covers the close quarters where elbows and short hooks live. A fighter who has tied up in the clinch, sprawled on a takedown, or caught an opponent ducking into a level change can use a knee to do significant damage in spaces too tight for a kick to land cleanly. The power source is the hip extending forward and upward, with body weight and momentum behind it.

How a knee strike works

The knee generates force through hip flexion. The back leg’s hip drives forward and up while the support leg’s heel rises onto the ball of the foot. Body weight transfers into the strike, and the impact lands through the kneecap or the area just above it.

Range determines the version a fighter throws. From a tight clinch, the knee can travel only a few inches and still carry significant power because of how much weight rides behind it. From mid-range, a fighter can step in or even leap, converting horizontal momentum into vertical force at impact. Targets shift accordingly: head and chin for stand-up exchanges, ribs and solar plexus to break the body, and thighs or hips to chip away at structure.

Recognising one in a fight comes down to two things: the angle (an upward drive rather than a horizontal swing) and the surface (point of impact at the knee rather than the shin or foot). Once those are clear, the type of knee tends to identify itself.

Types of knee strikes in MMA

Several knee variations show up regularly in MMA fights. The straight knee is the foundation; the others are angles and entries built around it.

Type	Muay Thai name	Description	Common range
Straight knee	Khao trong	Drives the front of the knee upward into the body or head	Clinch and close range
Curved or diagonal knee	Khao khong / khao chiang	Rotates the knee from outside-in, attacking ribs and the side of the body	Close clinch
Flying knee	Khao loi or hanuman thayarn	Jumping knee, often a sprint into a leap; high-risk, high-reward	Mid-range, against off-balance or charging opponents
Ground knee	(no Thai term)	Knee delivered from a top position such as side control or north-south	Ground top control

Wikipedia notes that the curved knee can be thrown from a much tighter distance than the straight knee, which makes it the preferred option once an opponent buries their head into the chest to defend.

The flying knee is the variation that gets the most attention. Anyone who watched UFC 239 in July 2019 saw why: Jorge Masvidal scored the fastest knockout in UFC history with one, finishing Ben Askren in five seconds. According to ESPN, Masvidal sprinted across the cage as soon as the bell rang and landed the knee as Askren ducked his head for a takedown attempt.

Knee strike rules in MMA

Most knees in MMA are legal. The exception, and the one that decides fights, is the rule against kneeing a grounded opponent in the head.

The UFC’s published Unified Rules list “kneeing and/or kicking the head of a grounded opponent” as a foul that may result in penalties or disqualification. The definition of “grounded,” though, has been one of the most argued points in the sport. Through the 2010s, US states applied different versions of the rule: in some, any body part other than the soles of the feet touching the canvas meant the fighter was grounded; in others, a fighter had to have both palms or fists on the mat.

That changed in 2024. According to CBS Sports, the Association of Boxing Commissions voted in July 2024 to amend the rule so that a fighter is grounded when any part of the body other than the hands or feet touches the canvas. The change removed the “palm-down trick” that some fighters used to instantly become grounded and avoid an incoming knee. UFC President Dana White confirmed the rule took effect at UFC Edmonton on November 2, 2024.

Knees to the body of a grounded opponent are legal under the Unified Rules, as are knees to the head of a standing opponent. ONE Championship, the Singapore-based promotion, uses its own Global Rule Set that allows knees to the head of a grounded opponent, a key point of difference flagged by Combat Sports Law when the rule set was approved for use in Colorado in 2021. UFC has not adopted that approach and continues to follow the Unified Rules.

For a deeper breakdown of which knees draw point deductions or disqualifications, see Speak-MMA’s guide to illegal knee strikes in MMA.

Knee strike vs kick: what’s the difference?

The two strikes share lower-body mechanics but solve different problems. A knee operates in close range and impacts with the kneecap or the soft area just above it. A kick operates at mid to long range and impacts with the shin or, in some variations, the top of the foot.

	Knee strike	Kick
Range	Close (clinch to inside punching range)	Mid to long
Impact surface	Kneecap and surrounding area	Shin (usually) or foot
Power source	Hip drive with body weight	Hip rotation through the full leg arc
Typical targets	Head, body, thighs at short distance	Legs, body, head from a distance
Common situations	Clinch, ducking opponent, takedown attempt	Distance striking, transitions, counter-striking

A flying knee blurs the line because it combines mid-range entry with knee impact, but the moment of contact still decides the classification. Shin or foot landing is a kick; knee landing is a knee.

Frequently Asked Questions

Are knee strikes legal in the UFC?

Yes, with restrictions. Knees to the head and body of a standing opponent are legal under the Unified Rules of MMA, but knees to the head of a grounded opponent are a foul. Knees to the body of a grounded opponent are legal.

What is a flying knee?

A flying knee is a knee strike thrown while jumping or leaping toward the opponent. In Muay Thai, it is called hanuman thayarn or khao loi. The added momentum makes it one of the most damaging strikes in combat sports when it connects clean.

What is the fastest UFC knockout, and what strike caused it?

Jorge Masvidal’s flying knee. At UFC 239 in July 2019, Masvidal sprinted across the cage at the bell and caught Ben Askren on a takedown attempt, ending the fight in five seconds. Guinness World Records lists it as the fastest knockout in UFC history.

Why are knees to the head of a grounded opponent illegal?

The rule exists to limit head trauma in vulnerable positions. A grounded fighter cannot defend or absorb impact the same way a standing fighter can, which raises the risk of serious injury. The Association of Boxing Commissions updated the definition of “grounded” in 2024 to make enforcement clearer across jurisdictions.

Where do knee strikes originate?

Knee strikes are traditional weapons of Southeast Asian martial arts, particularly Muay Thai, where they form one of the four pairs of striking tools in the art of eight limbs. They entered MMA largely through fighters with Muay Thai and kickboxing backgrounds.

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Sources

1. Wikipedia. “Knee (strike).” Accessed May 2026.
2. UFC. “Unified Rules of Mixed Martial Arts.” ufc.com. Accessed May 2026.
3. Brookhouse, Brent. “Commission removes 12-6 elbows from Unified MMA rules, updates grounded opponent rule.” CBS Sports, July 23, 2024.
4. Raimondi, Marc. “Masvidal’s 5-second KO fastest in UFC history.” ESPN, July 6, 2019.
5. Guinness World Records. “Fastest UFC KO.” guinnessworldrecords.com. Accessed May 2026.
6. Association of Boxing Commissions. “Unified Rules of Mixed Martial Arts.” abcboxing.com, 2019.
7. Heavy.com. “Explaining the New MMA Rules That Debuted at UFC Edmonton.” November 2024.
8. Magraken, Erik. “One Championship (And Knees To Grounded Opponents) Coming to Colorado?” Combat Sports Law, July 2021.

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