1 | 2 | 3 | 4 | 5 | 6    View All Up to 90% of auto accidents are rear end collisions. Therefore most people don't know the accident is about to happen, are not braced for the impact and the injuries are worse. Many accidents also cause injury to the TMJ (jaw) which can result in a popping, clicking or grinding of the joint; also TMJ injuries can cause ongoing headache symptoms and many times are overlooked. Many factors enter into the extent of injury: were vehicles of the same size or was the striking vehicle larger/heavier, was the struck vehicle moving or stopped, was the road condition wet, dry or iced over; was it a side impact, a direct rear end collision or an impact at the corner of the vehicle. Were headrests used, were they set at proper height.