Overview of Degenerative Disc Disease
Degenerative disc disease (DDD), also sometimes called spondylosis, is a condition characterized by damage to the invertebral discs. Invertebral discs are the gel-like cushions that separate each segment (vertebra) of the backbone or spine. Degenerative disc disease can result in pain and stiffness in the neck and/or back, as well as pain that spreads (radiates) to the back of the head, trunk, shoulders, arms, hands, legs, and feet.
Degenerative disc disease is actually a condition, not a disease—and the term "degenerative" does not imply that symptoms progressively worsen over time. In fact, in most cases, the condition stabilizes and symptoms gradually improve.
The spine is composed of thirty-three bony segments called vertebrae. There are seven segments in the neck (cervical vertebrae), twelve in the mid-back (thoracic vertebrae), and five in the lower back (lumbar vertebrae). The remainder of the segments forms the pelvis and tailbone.
In the cervical, thoracic, and lumbar spine, invertebral discs separate each vertebra. These discs, which absorb shock, consist of semi-fluid matter (nucleus pulposus) that is surrounded by a capsule of elastic fibers (annulus fibrosus) containing nerve endings. The vertebrae and the invertebral discs that separate each segment are designed to permit flexible support of the body and to protect the spinal cord and nerve roots from injury.
Invertebral discs have a minimal blood supply, which means they are not supplied with healing nutrients and oxygen and heal only minimally once they are damaged. Damage to the discs, either through traumatic injury or as a result of normal aging, causes the spine to weaken, leads to degenerative disc disease, and may result in pain.
Types of Degenerative Disc Disease
If disc degeneration occurs in one of the seven neck vertebrae, it is called cervical disc disease. Degeneration in the mid-back is called thoracic disc disease and is very uncommon. Degeneration in the vertebral discs of the lower back can cause low back pain called lumbago.
Incidence and Prevalence of Degenerative Disc Disease
Degenerative disc disease is a natural process of aging, and most people develop some degree of the condition over time. However, not all of these people experience related symptoms.
It is estimated that as many as 80% of all adults experience back pain at some point during their lifetime. Pain and impaired mobility associated with degenerative disc disease typically affects otherwise healthy adults between the ages of 30 and 50, although it can occur earlier. Degenerative disc disease rarely causes pain in people over the age of 65, but stiffness and decreased flexibility as a result of the condition are common in the elderly.