How Does a Punch to the Jaw Cause a Knockout?

A knockout blow, such as a punch to the jaw, brings a fighter to the ground and renders him unconscious or unable to defend himself. The opponent wins dramatically and the crowd may love it, but a KO causes trauma to the head that may result in injury to the brain.

Displacement of Brain

A fighter who cannot sustain a powerful punch to the jaw and is easily knocked out is said to have no chin or a glass jaw, according to boxing and mixed martial arts trainer Ross Enamait. A knockout punch snaps the head to the back or side and smashes the brain against the skull. The impact may traumatize the brainstem, resulting in loss of motor control. Blood supply to the brain can be cut off.

Force of the Blow

Impact to the brain is determined by the acceleration of the head and how forcefully it is snapped. Any blow to the head can cause a knockout, not just a punch to the jaw. The greater the force, the more quickly the head will turn following impact and the more the brain will be displaced and blood vessels compressed to the point of causing immediate unconsciousness.

Neck and Jaw Muscles

When an opponent is surprised by a blow to the head, his neck and jaw muscles are loose. If he is braced for the impact, a fighter can better absorb the impact of the punch, lessening the force of displacement. Some fighters have more stable jaws due to the anatomy they inherit but strengthening the neck muscles may help better handle impact to the jaw, according to "Fight Magazine" author Mike Chiappetta.


In boxing, a technical knockout usually requires 45 days off before a fighter returns to the ring, or he will be more susceptible to another knockout, according to Osric King, sports medicine physician and medical adviser for the New York State Athletic Commission. After a single knockout involving loss of consciousness, there needs to be a recovery period of at least 60 to 90 days. Chronic brain injury is more likely in cases of repeated blows to a boxer's head, according to the British Medical Association.