What Is Severe Degenerative Disc Disease?

Instructor: Robin Monegue Keeler

Robin has taught college microbiology and environmental science. She has two master's degrees: one in environmental microbiology and the other in public health.

In this lesson you will learn about the spine, the intervertebral discs, and how changes to the intervertebral disc result in severe degenerative disk disease, which is not really a disease at all.

Pain in the Neckā€¦and Back

You're able to sit, stand, walk, and bend thanks to your body's muscles, nerves, and bones - including your backbone. In fact, your backbone, or spinal column, is a major player in supporting these movements - and your body!

For some people who experience back pain (about eight out of ten adults have at least one episode of low back pain in their lifetime), the pain is due to degeneration (or deterioration resulting in a loss of function) of the intervertebral discs in the spine. The intervertebral discs are located between the vertebrae in your spine. (We'll talk about the spine, the discs, and the vertebra in more detail a bit later).

This degeneration is called degenerative disc disease (DDD). DDD is the deterioration of one or more intervertebral discs of the spinal column. It typically involves the low back (lumbar) or the neck (cervical) portions of the spine.

The Human Spinal Column
Spinal column

With severe degenerative disc disease (SDDD), the spine becomes unstable. This instability can lead to neurological symptoms such as pain or injury to the spinal cord. Additionally, a person's range of motion can be severely limited. Cases of SDDD may require surgical treatment to alleviate pain and stabilize the spine.

Despite the name, DDD is not a disease, but a normal part of aging. It's similar to getting gray hair or needing reading glasses as you age. The older you are, the more the disks in your back have undergone wear and tear. Additionally, the discs lose water as you get older, which makes them flatten. As a result, the discs lose their shock-absorbing function and don't cushion the vertebrae very well. This is especially true during physical activities like walking or running. Years of poor posture or even a significant back injury can also weaken the discs and cause their degeneration.

Let's briefly explore the spinal column and the intervertebral disks in a little more detail.

The Spinal Column

The spine is also called the spinal column. It provides the primary support for your body. Without it, you would not be able to stand upright, twist, or bend. The spinal column is made up of 33 bones that are stacked upon one another, which are called the vertebrae.

Located between each pair of vertebrae is a disc called an intervertebral disc. These discs act as shock-absorbing padding between each vertebra of the spine. They also allow the spine to be flexible. You can think of the intervertebral disc like a jelly-filled donut. The outer part of the disc is comprised of layers that connect and overlap, similar to the cake-like part of a jelly donut. This outer layer of the disk is called the annulus fibrosus; it's pretty tough and fibrous. The inner part of the disc is similar to the jelly in the donut - it's soft and gelatinous. This inner part is called the nucleus pulposus.

The Intervertebral Disc
Spinal Disc

Disc degeneration begins when the water content of the nucleus pulposus begins to decrease. In a healthy young adult, the discs are about 80-90% water. As you age, the water content decreases. Additionally, a molecule in the disc called proteoglycan also decreases. (Proteoglycan is found in connective tissues. Connective tissues provide support for the body's structures). When the intervertebral disc loses water and proteoglycan, the nucleus pulposus loses more of its ability to bear loads to the spine. As a consequence, the intervertebral discs flatten out and the annulus fibrosis is torn.

Example of a degenerated disc in the neck. (The fourth disc down from the top; notice it is thinner than the other discs.)
Degenerative disk disease, cervical

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