Under the age of 30, these discs are normally soft, and they act as cushions for the vertebrae. With age, the material in these lumbar discs becomes less flexible and the discs begin to erode, losing some of their height. As their thickness decreases, their ability to act as a cushion lessens. The less-dense cushion now alters the position of the vertebrae and the ligaments that connect them. In some cases, the loss of density can even cause the vertebra to shift its positions. As the vertebrae shift and affect the other bones, the nerves can get caught or pinched and muscle spasms can occur.

Degenerative disc disease is primarily a result of the normal aging process, but it may also occur as a result of trauma, infection, or direct injury to the disk. Heredity and physical fitness may also play a part in the process.