The phrase spinal segmental dysfunction refers to abnormal movement of a spinal motion segment. The abnormal movement may be passive or active. A spinal motion segment is defined as two adjacent vertebrae, the intervertebral disc between them, and the ligaments which support them. A spinal segment may move to much (hypermobile), may have limited movement (hypomobile), may move in an abnormal pattern (paradoxical movement) or it may not move at all (immobile or fixed. A normal spinal segment should have a little bounce detected with manual palpation. A loss of normal spinal segment joint play is a form of spinal segment hypomobility. Spinal segmental dysfunction can be further classified by whether there is associated reactive paraspinal muscle spasm when movement is evoked.
Spinal segment dysfunction can occur in individuals of all ages. There is no predilection between males or females. Trauma to the spine from a simple sprain strain to severe injury will cause a loss of normal intervertebral motion. Segmental dysfunction is likely to occur in the presence of degenerative changes of the spine therefore it is prevalent in elderly individuals.