Causes of Degenerative Disc Disease (DDD)
Degenerative disc disease (DDD) is primarily caused by age-related changes combined with genetic predisposition, with mechanical and occupational factors serving as significant contributors to accelerated degeneration. 1
Primary Causes
Age-Related Changes
- Normal aging process leads to progressive, irreversible changes in disc structure 2
- Gradual loss of water content in the nucleus pulposus
- Decreased proteoglycan synthesis
- Altered collagen distribution within the disc
Genetic Factors
- Genetics play a dominant role in determining susceptibility to disc degeneration 1
- Genetic polymorphisms affecting:
- Collagen structure and function
- Proteoglycan synthesis
- Inflammatory mediator production
- Disc matrix maintenance
Contributing Factors
Mechanical Influences
- Repetitive microtrauma to the disc structure
- Abnormal loading patterns that exceed the disc's physiological capacity
- Occupational factors:
- Heavy lifting
- Prolonged sitting
- Vibration exposure (e.g., truck driving)
- Poor ergonomics
Vascular Supply Issues
- Limited blood supply to intervertebral discs
- Progressive reduction in nutrient diffusion with age
- Accumulation of metabolic waste products
Inflammatory Processes
- Release of inflammatory mediators including:
- Tumor necrosis factor (TNF)
- Interleukins (IL-1β, IL-6, IL-8)
- These substances contribute to matrix degradation and pain generation 3
Pathophysiological Progression
Early Phase:
- Decreased water content in nucleus pulposus
- Reduced proteoglycan synthesis
- Initial microfissures in annulus fibrosus
Middle Phase:
- Loss of disc height
- Increased load on facet joints
- Annular tears progressing
- Ingrowth of blood vessels and nerve fibers into deeper layers of annulus 3
Late Phase:
- Significant structural compromise
- Potential for herniation, spinal stenosis, or spondylolisthesis
- Altered biomechanics affecting adjacent spinal structures 4
Clinical Implications
The pathological changes in DDD can lead to:
- Direct nociceptive pain from the disc itself (discogenic pain)
- Neuropathic pain from compression of neural structures
- Secondary pain from affected facet joints, ligaments, and muscles 3
Important Considerations
- MRI findings of disc degeneration correlate poorly with symptoms - many people with radiographic evidence of DDD remain asymptomatic 4
- The presence of degenerative changes should be interpreted with caution as they are common in patients over 30 years of age 4
- Central sensitization and neural plasticity play critical roles in the evolution of chronic pain related to DDD 3
Understanding the multifactorial etiology of DDD is essential for developing appropriate preventive strategies and treatment approaches that address both the structural and neurological aspects of this condition.