Permanent disability in some form occurs in approximately one in two cases after acute neck sprains. Whiplash injury normally occurs in rear end motor collisions, but may also result from front end or sideways crashes. Although seat belts will prevent serious crash injuries, they may actually increase the likelihood of neck sprains. The use of head restraints may prevent whiplash, but this is debatable, and their lack of effect could be due to lack of adjustability or inappropriate design. Between 75 per cent and 90 per cent of head restraints are incorrectly adjusted, most being in the fully down position.
Damage depends on the initial posture of the neck.
Sudden, unanticipated movements of the neck prevent the neck muscles from bracing in a reflex action. Pre-existing neck conditions and headaches often worsen after a car crash. A whiplash injury causes stretching and bruising of neck muscles and ligaments. This may, in turn, cause pain and stiffness extending into the shoulders and between the shoulder blades. Symptoms may take several hours to manifest.