Rear-end or side collisions often produce what is referred to as a whiplash injury. Muscles, ligaments, and cartilage in and around the neck can be injured by the sudden thrust of the head and neck forward and back.
Usually soft tissues of this kind take four to six weeks to heal. But it's not uncommon for two people in the same car to have different degrees of injury. Healing time can vary quite a bit. About one out of every three people in an auto accident has chronic pain months later.
Factors that can affect the injury include: the angle of the collision, the speed and size of the vehicles involved, and road conditions. Other things to consider include the position of the head and direction of the face at the time of the injury. Women seem to be at greater risk for injury than men. Anyone with other health issues can delay healing.