A neck injury that can occur when the head suddenly moves backward and then forward. This type of injury can occur, for example, during rear-end vehicle collisions. Injuries range from mild to severe. The main symptom is pain in the neck and shoulders. Treatment typically begins with over-the-counter pain relievers and ice. If the pain persists, treatment can include physiotherapy and prescription medication. In rare cases, injections into the neck may help. Whiplash is most commonly caused by a motor vehicle accident in which the person is in a car that is not moving, and is struck by another vehicle from behind. It is commonly thought the rear impact causes the head and neck to be forced into hyperextended (backward) position as the seat pushes the person's torso forward - and the unrestrained head and neck fall backwards. After a short delay the head and neck then recover and are thrown into a hyperflexed (forward) position. More recent studies investigating high-speed cameras and sophisticated crash dummies have determined that after the rear impact the lower cervical vertebrae (lower bones in the neck) are forced into a position of hyperextension while the upper cervical vertebrae (upper bones in the neck) are in a hyperflexed position. This leads to an abnormal S-shape in the cervical spine after the rear impact that is different from the normal motion. It is thought that this abnormal motion causes damage to the soft tissues that hold the cervical vertebrae together (ligaments, facet capsules, muscles).