The spine is held in place by supportive muscles, tendons and ligaments.The ligaments are tough, non-elastic bands that hold adjacent bones together and provide stability to the spine. The spine is capable of bearing a significant amount of weight as well as bending and twisting.Spinal movement occurs due to the flexibility of the intervertebral disc, the presence of the spinal facet joints and as the result of muscular contractions.

There is a numbering system used to identify the vertebra of the spine.Counting down from above, there are seven cervical vertebrae (neck), 12 thoracic vertebrae (mid-back) and five lumbar vertebrae (low back). The base of the spine is comprised of the sacrum and at the end of the sacrum; the coccyx (“tail bone�) is attached.The vertebral level capable of the greatest amount of rotation is the upper neck between the base of the skull and the second cervical vertebra.The low back is comprised of the L1 through L5 vertebrae which are typically the largest and strongest vertebrae within the spine.The low back or lumbar region supports the greatest amount of weight of any area of the spine.Extending from the neck to the coccyx, there are 31 pairs of nerve roots which exit the spinal canal, on the right or left side through openings in bone (foramina).

The back is complex, an intertwined network of muscles and ligaments which traverse up and down the spine and in between spinal segments.The spine provides stability during the upright posture and during walking, as well as other movements.The spine acts as a natural shock absorber via its curves and the mechanical relationship between each vertebra.