In the low back (as in other areas of the musculoskeletal system), the mechanical loading capacity of tissues lowers as we age. Because the low back is a hub of weightbearing, injuries can occur even with the simplest routine activities of daily living. This lifetime accumulation of such injuries, coupled with normal aging and degenerative processes, renders the back susceptible to re-injury. For example, the spinal segment can be viewed similar to a three-legged stool, with the front leg of the stool representing the intervertebral disc, and the back two legs of the stool represented by the right and left apophyseal joints. Apophyseal joint arthritis alone, or in combination with degeneration of the annulus fibrosus, results in an intervertebral segment that has less ability to tolerate forces such as tension, compression, and shear. Such degenerative changes result in the loss of inherent spinal stability. The breakdown of these tissues can result in aberrant motion between vertebral segments, resulting in segmental instability. Partial thickness degeneration of the facets of the apophyseal joints results in a segment that can no longer tolerate compressive loading when compared to normal, healthy tissue.7 When compression exceeds the physiological capacity of this compromised tissue, discomfort or pain results.