The mechanism of injury describes the particular circumstances that caused a given injury. Many medical professionals, including doctors and emergency medical technicians, are required to be familiar with a variety of circumstances that cause injury. Knowledge of the specific mechanism of injury can prepare a medical professional for the particular challenges that an injured patient may present. Emergency medical professionals often take various kinetic and physical details into consideration when assessing and describing the circumstances and causes of an injury. The mechanism of an injury from a car crash, for example, will often be described in terms of the speed, angle, and direction of the crash.
Mechanisms of injury are generally broken down into a variety of categories, such as motor vehicle accidents, rapid vertical decelerations, and penetrating trauma. These categories are further subdivided into many considerably more specific and useful descriptions of precisely what kind of injury occurred. Penetrating trauma, for instance, can be subdivided into stab wounds; firearm wounds; and other types of penetrative wounds, such as from falling onto sharp objects in one's work environment. These categories are often broken down even further, as an EMT or other emergency medical professional is able to respond more quickly to an injury if he is prepared with a highly accurate and specific way someone was injured. A mechanism of injury describing "a gunshot wound to the leg with a low-caliber weapon" is more useful than a vague description of "penetrating trauma."
Automobile accidents often require special attention if one is to accurately describe a mechanism of injury, as most automobile crashes take place in three phases, each of which can cause injury. In the first phase, vehicle impact, the automobile collides with another object, such as a street light or another automobile. In the second phase, body impact, the body of an individual in the automobile impacts with parts of the automobile, such as the windshield or steering wheel. Organ impact, the third phase, occurs when movable organs in one's body, such as the brain or intestines, collide with supporting organs, such as the rib cage or skull. Examining each phase of an accident can provide great insight into the nature and severity of the circumstances of the injury.
It is often necessary to examine the entire scene of an injury, not just the injured individual himself, in order to determine the mechanism of injury. A cracked windshield, for instance, may indicate that an individual in a car crash was not properly secured with a seat belt and that he flew from his seat and collided with the windshield. Severe outward signs of trauma may not be visible, but the cracked windshield may indicate the possibility of more severe internal trauma.