Pain from degenerative disc disease is typically caused by strain on the muscles supporting the spine and inflammation around the disc space.
Degeneration occurs because of age-related wear-and-tear on a spinal disc, and may be accelerated by injury, health and lifestyle factors, and possibly by genetic predisposition to joint pain or musculoskeletal disorders. Degenerative disc disease rarely starts from a major trauma such as a car accident. It is most likely due to a low-energy injury to the disc.
Lumbar Degenerative Disc Disease Causes
The low back pain associated with lumbar degenerative disc disease is usually generated from one or both of following sources:
- Inflammation, as the proteins in the disc space irritate the surrounding nerves—both the small nerve within the disc space and potentially the larger nerves that go to the legs (the sciatic nerve).
- Abnormal micro-motion instability, when the outer rings of the disc, called the annulus fibrosis, are worn down and cannot absorb stress on the spine effectively, resulting in movement along the vertebral segment.
Over a long period of time the pain from lumbar degenerative disc disease eventually decreases, rather than becoming progressively worse. This pain relief occurs because a fully degenerated disc no longer has any inflammatory proteins (that can cause pain) and usually collapses into a stable position, eliminating the micro-motion that generates the pain.
The Degenerative Cascade
When a disc endplate is damaged, the blood supply to the discs is compromised, leading to a lack of nutrients and oxygen that are essential for restoring damaged tissues. Once one stress or injury occurs, a disc can begin to wear down relatively quickly in a process called the degenerative cascade.
The degenerative cascade is a slow process that typically continues for 10 to 30 years and usually consists of the following cycle:
- An initial stress or injury may occur, causing acute pain that may be severe. Stiffness and limited mobility may occur immediately after the initial injury or stress to the disc. In many cases, there is no clear injury that causes the onset of symptoms.
- The affected spinal segment then undergoes a long period of relative instability. As the disc height decreases, the muscles, ligaments, and facet joints around the disc space gradually adjust to stabilize the spine again. During this phase, there are periodic flare-ups of moderate or intense low back pain.
- Once the spinal segment stabilizes, pain and other symptoms tend to alleviate.
It is common that back pain from degenerative disc disease is more severe between ages 30 and 40 than past age 60.
Risk Factors for Degenerative Disc Disease
Lifestyle factors that affect overall health can have an impact on the spinal discs. Risk factors for degenerative disc disease include:
- Family history of back pain or musculoskeletal disorders
- Excessive strain on the low back caused by sports, frequent heavy lifting, or labor-intensive jobs
- Strain on the lumbar spinal discs due to prolonged sitting and/or poor posture
- Lack of support for the discs due to weak core muscles
- Smoking, or any form of nicotine intake
Disc degeneration is a common part of aging, but not all people develop pain or any remarkable symptoms. Symptoms tend to arise when spinal instability, muscle tension, and possibly nerve root irritation occurs.