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Ingemar Johansson knocks Floyd Patterson out, becoming boxing heavyweight champion of the world, on June 26, 1959.
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 full-contact combat sports, such as boxing, kickboxing, muay thai, mixed martial arts, karate, some forms of taekwondo and other sports involving striking, as well as fighting-based video games. 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 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 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.[1] Even if the fighter loses consciousness for a brief moment and wakes up again to continue to fight, the fight is stopped and a KO is declared.[2] 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. 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 adhering to the rules of professional boxing, although technically they are classified as sports games, and share many of the same features as NFL and NBA video games.

Technical knockout[edit]

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).[3] Furthermore, in amateur boxing, a boxer automatically wins by TKO if his opponent is knocked down four times in an entire match.[4]

In MMA bouts, the referee may declare a TKO if a fighter cannot intelligently defend themselves while being repeatedly struck.[1]

Double knockout[edit]

A double knockout, both in real-life combat sports and in fighting-based video games, occurs when both fighters trade blows and knock each other out simultaneously and are both unable to continue fighting. In such cases, the match is declared a draw.

Physical characteristics[edit]

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 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 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 solar plexus.

A fighter who becomes unconscious from a 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 strokes or paralysis in the immediacy,[5] and over time have been linked to permanent neurodegenerative diseases such as chronic traumatic encephalopathy ("punch-drunk syndrome"). Because of this, many physicians advise against sports involving knockouts.[6]


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 a count by the referee (normally to 10); if the fighter fails the count, then the fight is ended as a KO.[7]

A flash knockdown is a knockdown in which the fighter hits the canvas but isn't noticeably hurt or affected.[7]

Knockout records[edit]

Top 10 boxers by most KOs[edit]

  1. Billy Bird (138)[8]
  2. Archie Moore (132)
  3. Young Stribling (129)
  4. Sam Langford (126)
  5. Buck Smith (120)
  6. Kid Azteca (114)
  7. George Odwell (111)[9]
  8. Sugar Ray Robinson, Alabama Kid (108)[10]
  9. Peter Maher (107)
  10. Sandy Saddler (103)

Top 10 boxing champions (including interims for WBA, WBC, WBO, or IBF) by KO percentage[edit]

Inactive National Boxing Association, World Colored Boxing.

  1. Edwin Valero, Artur Beterbiev, Subriel Matías (100%)
  2. Deontay Wilder (98%)
  3. Alfonso Zamora (97%)
  4. Jonathan Guzmán (96%)
  5. Carlos Zárate Serna, Wilfredo Gomez, Frank Bruno, Serhii Bohachuk (95%)
  6. Gerald McClellan, Gervonta Davis (93%)
  7. Danny Lopez, Lucas Matthysse, Yuniel Dorticos (92%)
  8. In-Chul Baek, Vitali Klitschko, Ángel Acosta (91%)
  9. Rafael Márquez, Jaron Ennis, David Morrell (90%)
  10. George Foreman, Julian Jackson, Aaron Pryor, Miguel Berchelt, Anthony Joshua (89%)
  11. Rubén Olivares, Shannon Briggs, Khaosai Galaxy, Mike Tyson, Rocky Marciano, Gennady Golovkin, Juan Manuel López, Marcos Maidana, Pipino Cuevas, Naoya Inoue (88%)

Top 10 MMA fighters by most KOs[edit]

  1. Travis Fulton (143)
  2. Igor Vovchanchyn (41)
  3. Travis Wiuff (39)
  4. Luís Santos (38)
  5. Joe Riggs (37)
  6. Paul Daley (35)
  7. Gilbert Yvel (35)
  8. Alexander Shlemenko (34)
  9. Mirko Filipovic (30)
  10. Melvin Manhoef (29)

Top 10 MMA (champions, challengers) fighters by KO percentage[edit]

Fighters from inactive Pride Fighting Championships and active UFC/Bellator plus champions and former champions from other organizations.

  1. Melvin Manhoef (91%)
  2. Jimi Manuwa (88%)
  3. Conor McGregor, Jiri Prochazka, Cain Velasquez, Yoel Romero, Gilbert Yvel (86%)
  4. Derrick Lewis (81%)
  5. Justin Gaethje (79%)
  6. Mirko Filipovic, Mauricio Rua (78%)
  7. Wanderlei Silva, Mark Hunt, Cristiane Justino Cody Garbrandt (77%)
  8. Stipe Miocic, Alex Pereira (75%)
  9. Anthony Johnson, Igor Vovchanchyn, Robbie Lawler (73%)
  10. Junior Dos Santos (68%)

Most consecutive KOs[edit]

Note: Considering Clark's unbeaten run of 42–0 with 42 knockouts, one should take into account he faced limited to no opposition; his first bout with a top-ten ranked opponent, who happened to be Bartolo Soni (12–2–1), ended with a TKO loss for him. Two other notable cases of highly questionable consecutive knockout records in boxing history were Peter McNeeley, running 36–1 with 30 knockouts before facing recently paroled Mike Tyson (41–1–0), and Richie Melito, who built up a record of 18–0 with 17 knockouts and was dubbed the "White Tyson" before Bert Cooper (34–17) stopped him.[12] Less notable but nevertheless mentionable cases include Don Steele, running 41–0 with 38 KOs before facing off Brian Nielsen (38–0), and Faruq Saleem, running 38–0 with 32 KOs before he faced casual actor Shawn McLean (3–4–0).

Most 1st round KOs and most consecutive 1st round KOs[edit]

Top 10 kickboxers by most KOs[edit]

  1. Changpuek Kiatsongrit (178)
  2. Frank Lobman (100)
  3. Toshio Fujiwara (99)
  4. Andy Souwer (98)
  5. Ramon Dekkers (95)
  6. Badr Hari (92)
  7. Fabrice Aurieng (89)
  8. Mike Zambidis (86)
  9. Branko Cikatic (82)
  10. Peter Aerts (81)

Top 10 Kickboxers (champions, challengers) by KO percentage[edit]

K-1, K-2 and Glory champions and Grand-Prix Winners as well as champions from other promotions.

  1. Andrew Thomson, Kevin Rosier (100%)
  2. Ginty Vrede (95%)
  3. Branko Cikatić (94%)
  4. Mite Yine, Dennis Alexio, Abiral Ghimire (93%)
  5. Besim Kabashi, Alain Ngalani (92%)
  6. Frank Lobman (91%)
  7. Benny Urquidez, Dustin Jacoby, Jean-Yves Theriault (90%)
  8. Nicholas Pettas (89%)
  9. Alessandro Riguccini (88%)
  10. Zack Mwekassa, Ben Edwards, Badr Hari, Jean-Claude Leuyer (87%)

Boxing's 50 knockout club (professional boxers with 50 or more knockouts)[edit]

See also[edit]


  1. ^ a b "Rules and Regulations - Unified Rules and Other MMA Regulations". www.ufc.com. Archived from the original on 2016-04-16.
  2. ^ http://mixedmartialarts.com/mma-news/341856/Herb-Dean-The-fight-is-over-when-hes-unconscious[permanent dead link]
  3. ^ "WBA Rules as Amended at Directorate Meeting in Orlando, Florida - December 2022" (PDF). WBA Boxing. Retrieved 2024-02-04.
  4. ^ Sugar, Bert. Boxing Archived 2006-06-19 at the Wayback Machine. www.owingsmillsboxingclub.com. URL last accessed March 4, 2006.
  5. ^ "Boxer gets record $22 million settlement from New York in brain injury case". mmafighting.com. 8 September 2017. Archived from the original on 2017-09-18.
  6. ^ Lieberman, Abraham (1 April 2005), Causing Parkinson: Boxing, Brain Injury, archived from the original on 15 May 2006, retrieved 24 June 2010
  7. ^ a b Boxing Terminology Archived 2012-06-25 at the Wayback Machine Ringside by Gus. URL last accessed June 17, 2008.
  8. ^ "Billy Bird". Archived from the original on 2014-10-18. Retrieved 2013-01-30.
  9. ^ "George Odwell". Archived from the original on 2014-10-18. Retrieved 2013-01-30.
  10. ^ "Alabama Kid". Archived from the original on 2014-10-18. Retrieved 2013-01-30.
  11. ^ "Boxing by the numbers". Archived from the original on 2012-12-15.
  12. ^ Newfield, Jack (November 12, 2001). "The Shame of Boxing: The fighters are powerless workers in need of rights and justice". The Nation. 273 (17): 20. ISSN 0027-8378.
  13. ^ "BoxRec: Kid Pascualito". Archived from the original on 2023-09-09. Retrieved 2020-08-12.

External links[edit]