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Ingemar Johansson knocks Floyd Patterson out, becoming boxing heavyweight champion of the world, on June 26, 1959. Ingemar Johansson and Floyd Pattersson 1959.JPG
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. Muhammad Ali fights Brian London on August 6, 1966.jpg
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 declared a KO. [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-based video games, such as Street Fighter and Tekken , a player scores a knockout by fully depleting the opponent's health bar, which awards the round to the winning player. The player who wins the most rounds (by scoring the most knockouts or by having more vitality remaining when time expires during each round) wins the match. This is different from real-life combat sports, where a knockout would end the match immediately.

Technical knockout

A boxer delivers a knockout blow to his opponent, prompting the referee to stop the fight. 2017-12-02 Roman Hardok - Jakob Jakobi - DSC2359.jpg
A boxer delivers a knockout blow to his opponent, prompting the referee to stop the fight.

A technical knockout (TKO or T.K.O.), or stoppage, 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 many regions, a TKO is declared when a fighter is knocked down three times in one round. [3]

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

Double knockout

A double knockout, both in real-life combat sports and in fighting-based video games, is 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. In fighting games such as Street Fighter , Dead or Alive and Tekken , a draw is counted as a loss for both players.

Physical characteristics

A knockout can be characterized by unconsciousness. SingletonBox-knockout.jpg
A knockout can be characterized by unconsciousness.

Little is known about 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 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 whether they cause loss of consciousness, are known to gradually cause permanent brain damage. In severe cases this may cause strokes or paralysis. [4] This loss of consciousness is commonly known as becoming "punch drunk" or "shot". Because of this, many physicians advise against sports involving knockouts. [5]


A boxer was knocked out, and is being inspected by a ring doctor. Box24-knock-down.jpg
A boxer was 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. [6]

A flash knockdown is a knockdown in which the fighter hits the canvas but recovers quickly enough that a count is not started. [6]

Knockout records

Top 10 boxers by most KOs

  1. Billy Bird (138) [7]
  2. Archie Moore (132)
  3. Young Stribling (129)
  4. Sam Langford (128)
  5. Buck Smith (120)
  6. Kid Azteca (114)
  7. George Odwell (111) [8]
  8. Sugar Ray Robinson, Alabama Kid (108) [9]
  9. Peter Maher (107)
  10. Sandy Saddler (103)

Top 10 boxing champions (including interims) by KO percentage

Inactive National Boxing Association, World Colored Boxing Championship as well as list on List of current world boxing champions and European Boxing Union.

  1. Edwin Valero, Artur Beterbiev, Ali Raymi (100%)
  2. Deontay Wilder, Gervonta Davis, Ángel Acosta (95%)
  3. Jonathan Guzmán (92%)
  4. Carlos Zárate Serna, Dmitry Kudryashov, Yuniel Dorticos, LaMar Clark (90%)
  5. Anthony Joshua, Rocky Marciano, Wilfredo Gómez, Aaron Pryor, Laila Ali, Gary Mason (88%)
  6. Vitali Klitschko, Gennady Golovkin, Errol Spence Jr., Naoya Inoue, Jaime Munguia (87%)
  7. Khaosai Galaxy (86%)
  8. Eduard Troyanovsky, Oleksandr Gvozdyk, Gerald McClellan, Miguel Berchelt, In-Chul Baek, David Benavidez (85%)
  9. Naseem Hamed, Alfonso Zamora, Frank Bruno, David Haye, George Foreman, Alberto Machado (84%)

Top 10 MMA fighters by most KOs

  1. Travis Fulton (115)
  2. Igor Vovchanchyn (41)
  3. Travis Wiuff (39)
  4. Joe Riggs (37)
  5. Gilbert Yvel (34)
  6. Alexander Shlemenko (32)
  7. Paul Daley (31)
  8. Mirko Filipovic (30)
  9. Melvin Manhoef (29)
  10. Wanderlei Silva (27)

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

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

  1. Melvin Manhoef (93.33%)
  2. Derrick Lewis (88.89%)
  3. Jimi Manuwa (88.23%)
  4. Mark Hunt (87.50%)
  5. Conor McGregor (81%)
  6. Cristiane Justino (76.43%)
  7. Cain Velasquez (73.33%)
  8. Yann Decoopman (72%)
  9. Thiago Santos, Junior Dos Santos (71%)

Most consecutive KOs

Most 1st round KOs and most consecutive 1st round KOs

Top 10 K-1 and K-2 kickboxers by most KOs

  1. Changpuek Kiatsongrit (178)
  2. Andy Souwer (98)
  3. Ramon Dekkers (95)
  4. Badr Hari (92)
  5. Mike Zambidis (86)
  6. Branko Cikatic (82)
  7. Manson Gibson (80)
  8. Peter Aerts (79)
  9. Rob Kaman (77)
  10. Buakaw Banchamek, Tyrone Spong (73)

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

See also

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