Healthy intervertebral discs are composed of approximately 80% water at birth, with a gel-like nucleus pulposus that absorbs shock and distributes load evenly across the spine. Over time, the disc's water content declines steadily, often dropping below 70% by age 50. This desiccation reduces the disc's ability to cushion vertebral bodies, leading to height loss and compromised flexibility throughout the spinal column.
As discs lose height, the vertebrae move closer together, altering spinal biomechanics and placing uneven pressure on facet joints, ligaments, and surrounding nerve structures. This mechanical shift can trigger inflammation, muscle spasm, and the formation of bone spurs (osteophytes) as the body attempts to stabilize the compromised segment, often resulting in the stiffness and pain characteristic of DDD.
The disc's nutrient supply depends on a diffusion process through the vertebral endplates, since adult discs have virtually no direct blood supply. When these endplates calcify or become damaged through repetitive loading, nutrient delivery to the disc interior diminishes, accelerating cellular death and structural breakdown in a cycle that compounds over time.
