Degenerative disc disease refers to the condition where the intervertebral discs, which act as flexible cushions between the vertebrae in the spine, deteriorate or wear down over time. These discs are composed of a tough outer layer (annulus fibrosus) and a gel-like inner core (nucleus pulposus), serving to absorb shock, allow for spinal movement, and maintain space between the vertebrae.

As a person ages, the intervertebral discs gradually lose water content and elasticity, becoming thinner and less able to provide proper cushioning and support to the spine. This degeneration can lead to various symptoms such as back pain, stiffness, reduced flexibility, and, in some cases, nerve compression resulting in radiating pain, numbness, or weakness in the limbs.