What Causes Spondylosis?
Spondylosis is fundamentally caused by age-related degenerative changes in the intervertebral discs and facet joints of the spine, representing a chronic, noninflammatory disease process that affects the structural integrity of spinal elements. 1, 2, 3
Primary Degenerative Mechanisms
The core pathophysiology involves progressive degeneration of two key anatomical structures:
- Intervertebral disc degeneration is the primary initiating factor, where the disc loses water content, height, and structural integrity over time 1, 3
- Facet joint degeneration occurs as a secondary consequence, with these joints bearing increased mechanical stress as disc height diminishes 3
- Osteophyte formation develops as a compensatory response to instability, with bone spurs forming at vertebral margins and potentially compromising the spinal canal diameter 3
Multifactorial Etiology
The development of spondylosis involves multiple contributing factors beyond simple aging:
Genetic Predisposition
- Familial inheritance patterns have been documented, with first-degree relatives showing similar locations and severity of cervical spondylosis 4
- Genetic factors determine spinal shape, and similar spines tend to degenerate in similar patterns, suggesting hereditary susceptibility 4
- HLA-B27 association is relevant specifically for inflammatory spondyloarthropathies (ankylosing spondylitis), which represents a distinct inflammatory process rather than degenerative spondylosis 5, 6
Biomechanical Factors
- Mechanical stress transmission through discs and facets during normal spine mobility accelerates degenerative changes 3
- Congenital spinal stenosis (developmentally short pedicles) predisposes individuals to earlier symptomatic compression when degenerative changes occur 7
- Spinal malalignment can accelerate focal degenerative changes at specific levels 5
Age-Related Changes
- Middle-aged and elderly populations are predominantly affected, with spondylosis representing the most common progressive disorder in the aging cervical spine 2, 3
- Degenerative disc disease is essentially universal with advancing age, though not all individuals become symptomatic 5, 1
Important Clinical Distinctions
It is critical to distinguish degenerative spondylosis from inflammatory spondyloarthropathies:
- Degenerative spondylosis is noninflammatory, age-related, and affects discs and facets 1
- Ankylosing spondylitis (inflammatory spondyloarthropathy) involves enthesitis, synovitis, and osteitis with strong HLA-B27 association, typically presenting before age 45 with inflammatory back pain 5
- These are fundamentally different disease processes with different etiologies, despite similar terminology 5
Pathophysiological Consequences
The degenerative cascade leads to specific anatomical changes:
- Spinal canal narrowing results from posterior osteophyte formation, ligamentum flavum hypertrophy, and facet joint hypertrophy 5, 3
- Neural foraminal stenosis develops from uncovertebral joint hypertrophy and facet hypertrophy, potentially causing radiculopathy 5
- Disc bulging or herniation may occur as disc integrity fails, contributing to nerve root or cord compression 5, 2
Common Clinical Pitfall
A critical caveat: spondylotic changes on imaging correlate poorly with symptoms. Radiographic and MRI evidence of spondylosis is commonly found in asymptomatic individuals over age 30, making it essential to correlate imaging findings with clinical presentation before attributing symptoms to degenerative changes 5, 8. The presence of spondylosis on imaging does not automatically explain a patient's pain or neurological symptoms.