Last week I was sitting in my car at a red light when someone rear-ended me. The car that hit me was only going 20 miles per hour, but it caused considerable damage to my car. At the time of the accident, I felt fine. But the next day, I woke up with a headache and neck pain that hasn't gone away. Why is that?

Scientists are still studying the mechanisms of damage to the neck and surrounding tissues after a rear-end collision. Researchers have been able to show that during the impact, the bones of the upper neck are forced to move abnormally, causing tissue injury. There may also be pressure on one or more nerves as they exit the spine in the neck region. This can cause the kind of pain that starts in the neck and travels down the arm.

The joints of the neck may also slide and get compressed during a rear-end collision. This can cause neck joint pinching and possible damage. It remains unknown why some people have symptoms for a few days and others continue to have problems weeks and even months later. Tell your doctor about your symptoms and see what he or she recommends.