Center for Injury Research and Prevention

The Knockout Game: Recreational Assault and Traumatic Brain Injury

TitleThe Knockout Game: Recreational Assault and Traumatic Brain Injury
Publication TypeJournal Article
Year of Publication2014
AuthorsZonfrillo MR, Fein JA, Arbogast KB
JournalThe Lancet
Start Page513
Date Published02/2014
Type of Articleletter
Full Text
A recent trend in unprovoked, recreational assault resulting in traumatic brain injury and death of innocent bystanders has many pseudonyms including knockout, knockout king, bombing, bomb, polar-bearing, polar-bear hunting, and happy slapping. While media reports of this type of assault vary, it typically involves either one forceful punch to the head or a more generalised assault to a random individual (typically standing or walking alone) without any warning or provocation, and without any ulterior motive such as theft or retaliation. Instead, the overall goal of the game is to result in the victim's unconsciousness, and assailants might video record the assault and boast about their involvement for notoriety. Given that many assaults occur in public places, surveillance videos often capture the incidents and are subsequently used in media reports or as criminal evidence to identify and prosecute assailants, nearly all of whom are teenage boys. Medical case reports and boxing and fighting matches support the mechanism of a single blow to the head or neck resulting in temporary unconsciousness, coma, or death.1 These injuries typically include profound autonomic dysfunction with disruption of the reticular activating system, but often without intracranial haemorrhage.

It is challenging to identify the overall incidence of the knockout game. Not all apprehended assailants endorse their assault as part of the game and these assaults might not be captured by video or identified as a result of the game. Although the medical literature does not describe “knockout” by name, internet queries identify six reported deaths as a result of the game, all involving head injury in adult victims, one with a secondary spinal cord injury, and another with a penetrating injury of the heart. Additionally, a search in the US National Violent Death Reporting System database for fatal injuries by a stranger assailant using only hands or feet as a method of assault yields ten or fewer cases annually for 2005—10.2 Although social media has focused recent attention on the game and its increasing popularity, there is long-standing evidence for this intentional, unprovoked violence.3 The assault might fulfil certain psychological needs for the assailant, despite the random victim selection.4 There is additional concern that some attacks are targeted hate crimes, which has prompted community leaders and anti-crime groups to convene and discuss comprehensive mitigation strategies.5 Public awareness of the knockout game and further understanding of assailants' motives are crucial to prevent future assaults, injuries, and deaths.

We declare that we have no conflicts of interest.


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a Center for Injury Research and Prevention, Division of Emergency Medicine, Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA
b Department of Pediatrics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA