The spine consists of multiple segments of bone (vertebral bodies) in between which are intervertebral discs (behaving like shock absorbers). Behind these structures are the spinal cord or nerves. Behind the nerves are the joints of the spine (termed facet joints). With age, the discs undergo changes in their chemical composition causing it to lose its water content as well as disc height. This can cause additional stress on the facet joints causing arthritic changes of the joints. Back pain can be a symptom of spine degeneration. In some cases, the vertebral bodies can slip (termed degenerative spondylolisthesis). In those cases, nerves in the spine can be compressed causing pain, tingling or numbness in the legs. Terms like radiculopathy or claudication may sometimes be used to describe these symptoms.