There are normal curves in the neck and low back called lordosis that help provide flexibility to the spine. Following an auto accident, these curves can flatten out due to injury to ligaments of the spine. Flattening out of these curves helps to reduce shear forces, which can lead to sliding of the bones with reduced ligament support.
However, this can lead to problems as the benefits of the lordosis in the neck and low back are lost when the neck and back curves flatten. These lordosis normally reduce the muscle effort required to hold the body upright, as well as cushion the spine from impact during activities. When the lordotic curves of the neck and back flatten out and decrease, the center of body mass moves forward. To keep your body upright and in balance, the muscles of the back work harder and this results in increased compressive force on the discs of the spine.