View source for Knockout

{{short description|Fight-ending, winning criterion in certain full-contact combat sports}}
{{redirect2|KO|K.O.||Knockout (disambiguation)|and|KO (disambiguation)}}
[[File:Ingemar Johansson and Floyd Pattersson 1959.JPG|right|200px|thumb|[[Ingemar Johansson]] knocks [[Floyd Patterson]] out, becoming boxing [[heavyweight]] champion of the world, on June 26, 1959.]]
[[File:Muhammad Ali fights Brian London on August 6, 1966.jpg|right|200px|thumb|A heavy blow to the head is a frequent cause of a knockout. [[Muhammad Ali]] delivers one to [[Brian London]] and retains his heavyweight championship by third-round KO on August 6, 1966.]]
A '''knockout''' (abbreviated to '''KO''' or '''K.O.''') is a fight-ending, winning criterion in several [[Contact sports|full-contact]] [[combat sport]]s, such as [[boxing]], [[kickboxing]], [[Muay Thai]], [[mixed martial arts]], [[karate]], some forms of [[World Taekwondo Federation#Sparring|taekwondo]] and other sports involving [[strike (attack)|striking]], as well as [[fighting game|fighting]]-based [[video game]]s. A full knockout is considered any legal strike or combination thereof that renders an opponent unable to continue fighting.

The term is often associated with a sudden traumatic [[Unconsciousness|loss of consciousness]] caused by a physical blow. Single powerful blows to the head (particularly the jawline and temple) can produce a [[cerebral concussion]] or a [[carotid sinus reflex]] with [[Syncope (medicine)#Blood pressure|syncope]] and cause a sudden, dramatic KO. Body blows, particularly the [[liver punch]], can cause progressive, debilitating pain that can also result in a KO.

In boxing and kickboxing, a knockout is usually awarded when one participant falls to the canvas and is unable to rise to their feet within a specified period of time, typically because of exhaustion, pain, disorientation, or [[unconsciousness]]. For example, if a boxer is knocked down and is unable to continue the fight within a ten-second count, they are counted as having been knocked out and their opponent is awarded the KO victory.

In mixed martial arts (MMA) competitions, no time count is given after a knockdown, as the sport allows [[submission grappling]] as well as [[ground and pound]]. If a fighter loses consciousness ("goes limp") as a result of legal strikes, it is declared a KO.<ref name=ufc>{{cite web|url=http://www.ufc.com/discover/sport/rules-and-regulations#17|title=Rules and Regulations - Unified Rules and Other MMA Regulations|website=www.ufc.com|url-status=live|archive-url=https://web.archive.org/web/20160416102122/http://www.ufc.com/discover/sport/rules-and-regulations#17|archive-date=2016-04-16}}</ref> Even if the fighter loses consciousness for a brief moment and wakes up again to continue to fight, the fight may be stopped and a KO declared.<ref>http://mixedmartialarts.com/mma-news/341856/Herb-Dean-The-fight-is-over-when-hes-unconscious{{dead link|date=May 2018 |bot=SheriffIsInTown |fix-attempted=yes }}</ref> As many MMA fights can take place on the mat rather than standing, it is possible to score a KO via ground and pound, a common victory for [[grapplers]]. 

In [[fighting games]] such as ''[[Street Fighter]]'' and ''[[Tekken]]'', a player scores a knockout by fully depleting the opponent's [[health bar]], with the victor being awarded the round. The player who wins the most rounds, either by scoring the most knockouts or by having more vitality remaining when time expires during each round, wins the match. In some fighting games like Soul Calibur as well as platform fighters like Super Smash Bros, the player can also score a KO when the opponent fall off the fighting area. This differs from combat sports in reality, where a knockout ends the match immediately. However, some fighting games aim for a more realistic experience, with titles like ''[[Fight Night (video game series)|Fight Night]]'' adhering to the rules of professional boxing, although technically they are classified as [[sports video game|sports games]], and share many of the same features as [[NFL]] and [[NBA]] video games.

==Technical knockout<span class="anchor" id="Technical knockout"></span> ==
<!-- "RSC" (disambiguation page), "Referee stopped contest", and "Referee Stopped Contest" link here -->
{{redirect|TKO}}
[[File:2017-12-02 Roman Hardok - Jakob Jakobi - DSC2359.jpg|right|250px|thumb|The referee may stop a match if they deem either competitor unable to fight.]]
A '''technical knockout''' ('''TKO''' or '''T.K.O.'''), '''stoppage''', or '''referee stopped contest (RSC)''' is declared when the referee decides during a round that a fighter cannot safely continue the match for any reason.  Certain sanctioning bodies also allow the official attending physician at ringside to stop the fight as well.  In amateur boxing, and in many regions professionally, including championship fights sanctioned by the [[World Boxing Association]] (WBA), a TKO is declared when a fighter is knocked down three times in one round (called an "automatic knockout" in WBA rules).<ref>{{cite web |title=WBA Rules as Amended at Directorate Meeting in Orlando, Florida - December 2022 |url=https://www.wbaboxing.com/wp-content/uploads/2023/11/WBA-Rules-11.08.2023.pdf |website=WBA Boxing |access-date=2024-02-04 |ref=WBAKO}}</ref>  Furthermore, in amateur boxing, a boxer automatically wins by TKO if his opponent is knocked down four times in an entire match.<ref>Sugar, Bert. {{usurped|1=[https://web.archive.org/web/20060619215358/http://www.owingsmillsboxingclub.com/boxing.htm Boxing]}}. ''www.owingsmillsboxingclub.com''. URL last accessed March 4, 2006.</ref><ref name="WBCompetition">{{cite web |title=World Boxing Competition Rules |url=https://worldboxing.org/wp-content/uploads/2024/09/World-Boxing-Competition-Rules-Feb-2024-v3.99-ClEAN.pdf |website=World Boxing |access-date=2024-12-02}}</ref>

In MMA bouts, the referee may declare a TKO if a fighter cannot intelligently defend themselves while being repeatedly struck.<ref name=ufc/>

== Double knockout<span class="anchor" id="Double knockout"></span> ==
<!-- "Double knockout" links here -->
A '''double knockout,''' both in real-life [[combat sports]] and in [[fighting game|fighting]]-based [[video game]]s, occurs when both fighters trade blows and knock each other out simultaneously and are both unable to continue fighting.

In amateur boxing, a double knockout result is determined based on the round of competition.  In all contests ''except'' the final, both fighters are declared to have lost the contest and are eliminated, since a boxer is suspended 30-540 days for a knockout under boxing regulations.  In the final, where there must be a winner, the contest ends as if the bell sounded at the end of the final round, and the round is scored, with the winner determined by points. However, if both boxers are downed, both rise up, but one has reached the limit of knockdowns, the winning boxer is the one who has not reached the three/four knockdown limit.<ref name="WBCompetition" />

==Physical characteristics==
[[File:SingletonBox-knockout.jpg|thumb|A knockout can be characterized by unconsciousness.]]
Little is known as to what exactly causes one to be knocked unconscious, but many agree it is related to trauma to the [[Brainstem|brain stem]]. This usually happens when the head rotates sharply, often as a result of a strike. There are three general manifestations of such trauma:
* a typical knockout, which results in a sustained (three seconds or more) loss of consciousness (comparable to general anesthesia, in that the recipient emerges and has lost memory of the event).
* a "flash" knockout, when a very transient (less than three seconds) loss of consciousness occurs (in the context of a knock-down) and the recipient often maintains awareness and memory of the combat.
* a "stunning", a "dazing" or a fighter being "out on his feet", when basic consciousness is maintained (and the fighter never leaves his feet) despite a general loss of [[awareness]] and extreme distortions in [[proprioception]], balance, visual fields, and auditory processing. Referees are taught specifically to watch for this state, as it cannot be improved by sheer willpower and usually means the fighter is already [[concussion|concussed]] and unable to safely defend themselves.

A basic principle of boxing and other combat sports is to defend against this vulnerability by keeping both hands raised about the face and the chin tucked in. This may still be ineffective if the opponent punches effectively to the [[Celiac_plexus|solar plexus]].

A fighter who becomes unconscious from a [[strike (attack)|strike]] with sufficient [[knockout power]] is referred to as having been ''knocked out'' or ''KO'd'' (''kay-ohd''). Losing balance without losing consciousness is referred to as being ''knocked down'' ("down but not out"). Repeated blows to the head, regardless of whether they cause loss of consciousness, may in severe cases cause [[stroke]]s or [[paralysis]] in the immediacy,<ref>{{cite web|url=https://www.mmafighting.com/2017/9/8/16279100/boxer-gets-record-22-million-settlement-from-new-york-in-brain-injury-case|title=Boxer gets record $22 million settlement from New York in brain injury case|website=mmafighting.com|date=8 September 2017|url-status=live|archive-url=https://web.archive.org/web/20170918064225/https://www.mmafighting.com/2017/9/8/16279100/boxer-gets-record-22-million-settlement-from-new-york-in-brain-injury-case|archive-date=2017-09-18}}</ref> and over time have been linked to permanent [[neurodegenerative disease]]s such as [[chronic traumatic encephalopathy]] ("punch-drunk syndrome"). Because of this, many physicians advise against sports involving knockouts.<ref>{{citation |last1=Lieberman |first1=Abraham |archive-url=https://web.archive.org/web/20060515025923/http://www.liebermanparkinsonclinic.com/content/view/48/31/ |archive-date=15 May 2006 |title=Causing Parkinson: Boxing, Brain Injury |date=1 April 2005 |access-date=24 June 2010 |url=http://www.liebermanparkinsonclinic.com/content/view/48/31/}}</ref>

==Knockdown==
[[File:Box24-knock-down.jpg|thumb|right|275px|A boxer has been knocked out and is being inspected by a ring doctor.]]
A '''knockdown''' occurs when a fighter touches the floor of the ring with any part of the body other than the feet following a hit, but is able to rise back up and continue fighting. The term is also used if the fighter is hanging on to the ropes, caught between the ropes, or is hanging over the ropes and is unable to fall to the floor and cannot protect himself. A knockdown triggers [[Mandatory eight count|a count]] by the referee (normally to 10); if the fighter fails the count, then the fight is ended as a KO.<ref name="Boxing Terminology">[http://www.ringsidebygus.com/boxing-terms.html#k Boxing Terminology] {{webarchive|url=https://web.archive.org/web/20120625131941/http://www.ringsidebygus.com/boxing-terms.html |date=2012-06-25 }} ''Ringside by Gus''. URL last accessed June 17, 2008.</ref>

A '''flash knockdown''' is a knockdown in which the fighter hits the canvas but is not noticeably hurt or affected.<ref name="Boxing Terminology"/>

==Boxing's 50 knockout club (professional boxers with 50 or more knockouts)==
{{refimprove|date=September 2024}}
{{div col|colwidth=20em}}
* [[Billy Bird]] 138<ref name="bird">{{Cite web |title=Billy Bird|url=https://boxrec.com/en/box-pro/17871|website=BoxRec|access-date=10 September 2025}}</ref><ref name="sportster">{{Cite web |title=Boxers With the Most Knockouts|url=https://www.thesportster.com/boxers-with-the-most-knockouts/|website=TheSportster|access-date=10 September 2025}}</ref><ref name="fight">{{Cite web |title=Most Knockouts in Boxing|url=https://www.fightmma.org/most-knockouts-in-boxing/|website=FightMMA|access-date=10 September 2025}}</ref>
* [[Archie Moore]] 132<ref name="archie">{{Cite web |title=Archie Moore page 2|url=https://boxrec.com/en/box-pro/8995?&offset=100
|website=BoxRec|access-date=21 July 2025}}</ref><ref name="sportster"/><ref name="fight"/>
* [[Young Stribling]] 126<ref name="young">{{Cite web |title=Young Stribling|url=https://boxrec.com/en/box-pro/12052|website=BoxRec|access-date=10 September 2025}}</ref><ref name="sportster"/><ref name="fight"/>
* [[Sam Langford]] 126<ref name="sportster"/><ref name="fight"/>
* [[Buck Smith]] 120<ref name="sportster"/><ref name="fight"/>
* [[Kid Azteca]] 114<ref name="sportster"/><ref name="fight"/>
* [[George Odwell]] 111<ref name="sportster"/><ref name="fight"/>
* [[Sugar Ray Robinson]] 109<ref name="sportster"/><ref name="fight"/>
* Clarence Reeves 108<ref name="sportster"/><ref name="fight"/>
* [[Peter Maher (boxer)]] 107<ref name="sportster"/><ref name="fight"/>
* [[Sandy Saddler]] 103<ref name="sportster"/><ref name="fight"/>
* [[Henry Armstrong]] 101<ref name="sportster"/><ref name="fight"/>
* [[Joe Gans]] 100<ref name="sportster"/><ref name="fight"/>
* [[Jimmy Wilde]] 98<ref name="fight"/>
* [[Len Wickwar]] 94
* [[Jorge Castro (boxer)]] 90<ref name="fight"/>
* [[Tiger Jack Fox]] 89<ref name="fight"/>
* [[Jock McAvoy]] 88
* [[Julio César Chávez]] 86
* [[Yori Boy Campas]] 83
* [[Chalky Wright]] 83
* [[Tommy Freeman (boxer)|Tommy Freeman]] 83
* [[Jose Luis Ramirez]] 82
* [[Charles Ledoux]] 81
* [[Ted Kid Lewis]] 80
* [[Fritzie Zivic]] 80
* [[Rubén Olivares]] 79
* [[George Godfrey (boxer born 1897)|George Godfrey]] 77
* [[George Chaney]] 76
* [[Torpedo Billy Murphy]] 76
* [[Ceferino Garcia]] 74
* [[Lee Savold]] 72
* [[Primo Carnera]] 72
* [[Benny Bass]] 72
* [[Rodolfo Gonzalez (boxer)]] 71
* [[Tommy Ryan]] 71
* [[Roberto Durán]] 70
* [[Benny Leonard]] 70
* [[Earnie Shavers]] 70
* [[Jesus Pimentel]] 68
* [[Fred Fulton]] 68
* [[George Foreman]] 68
* [[Joe Jeanette]] 68
* [[Lou Brouillard]] 67
* [[Tommy Gomez]] 67
* [[Pedro Carrasco]] 66
* [[Billy Petrolle]] 66
* [[Marcel Cerdan]] 66
* [[Jack Dillon]] 66
* [[Willie Pep]] 65
* [[Elmer Ray]] 64
* [[George Chuvalo]] 63
* [[Carlos Zárate Serna]] 63
* [[Frank Moody]] 63
* [[Martín Vargas]] 63
* [[Eduardo Lausse]] 62
* [[Alexis Argüello]] 62
* [[Jack Kid Berg]] 61
* [[Barbados Joe Walcott]] 61
* [[Larry Gains]] 61
* [[Adilson Rodrigues]] 61
* [[Mickey Walker (boxer)]] 60
* [[Freddie Steele]] 60
* [[Ike Williams]] 60
* [[Cleveland Williams]] 60
* [[Gregorio Peralta]] 60
* [[Tami Mauriello]] 60
* [[Max Baer (boxer)]] 59
* [[Young Peter Jackson (boxer, born 1877)|Young Peter Jackson]] 59
* [[Carlos Monzon]] 59
* [[Joe Knight (boxer)]] 59
* [[Ricardo Moreno]] 59
* [[Panama Al Brown]] 59
* Kid Pascualito 59<ref>{{Cite web|url=https://boxrec.com/en/proboxer/9496|title=BoxRec: Kid Pascualito|access-date=2020-08-12|archive-date=2023-09-09|archive-url=https://web.archive.org/web/20230909122759/https://boxrec.com/en/proboxer/9496|url-status=live}}</ref>
* [[James Red Herring]] 58
* [[Eric Esch]] 58
* [[Tony Galento]] 57
* [[John Henry Lewis]] 57
* [[Pascual Perez (boxer)|Pascual Perez]] 57
* [[Charley White]] 57
* [[Kid Williams]] 57
* [[Len Harvey]] 57
* [[Jose Luis Castillo]] 57
* [[Bob Fitzsimmons]] 57
* [[Tiger Flowers]] 56
* [[Georges Carpentier]] 56
* [[Pedro Montanez]] 56
* [[Irish Bob Murphy]] 56
* [[Charles Kid McCoy]] 55
* [[Dixie Kid]] 55
* [[Gorilla Jones]] 55
* [[Freddie Mills]] 55
* [[Manuel Ortiz (boxer)|Manuel Ortiz]] 54
* [[Marcel Thil]] 54
* [[Solly Krieger]] 54
* [[Jose Napoles]] 54
* [[Bennie Briscoe]] 53
* [[Obie Walker]] 53
* [[Peter Kane]] 53
* [[Wladimir Klitschko]] 53
* [[Shannon Briggs]] 53
* [[Eugene Criqui]] 53
* [[Joe Louis]] 52
* [[Mike McTigue]] 52
* [[Philadelphia Jack O'Brien]] 52
* [[Lew Jenkins]] 52
* [[Marvelous Marvin Hagler|Marvin Hagler]] 52
* [[Rocky Graziano]] 52
* [[Ezzard Charles]] 52
* [[Arturo Godoy]] 52
* [[Kid Chocolate]] 51
* [[Packey McFarland]] 51
* [[Jimmy Slattery]] 51
* [[Abe Attell]] 51
* [[Miguel Angel Castellini]] 51
* [[Jorge Vaca]] 51
* [[Jorge Paez]] 51
* [[Marco Antonio Rubio]] 51
* [[Charley Burley]] 50
* [[Jose Legra]] 50
* [[Eder Jofre]] 50
{{div col end}}

==See also==
{{portal|Martial arts}}
* [[Boxing styles and technique]]
* [[Chin (combat sports)]]
* [[Full contact karate]]
* [[Punch (combat)]]
* [[Punching power]]
* [[Taekwondo]]

==References==
{{reflist|30em}}
{{Combat sports decisions}}
{{Mixed martial arts}}
{{Boxing}}

[[Category:Martial arts terminology]]
[[Category:Boxing rules and regulations]]