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 process, 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 genetic factors determining spinal shape and predisposing certain individuals to similar degenerative patterns 4
- HLA-B27 association is relevant specifically for inflammatory spondyloarthropathies (ankylosing spondylitis), which represent a distinct disease entity from degenerative spondylosis 5, 6
Biomechanical Factors
- Mechanical stress transmission through the disc-facet complex accelerates degeneration, particularly at mobile segments like C5-6 and C6-7 in the cervical spine 3
- Congenital spinal stenosis (developmentally short pedicles) predisposes to earlier symptomatic compression when combined with degenerative changes 7, 2
- Repetitive loading and motion at specific spinal levels contributes to accelerated wear patterns 3
Age-Related Changes
- Progressive disc desiccation occurs universally with aging, though the rate varies significantly between individuals 2, 3
- Middle-aged and elderly populations are predominantly affected, with radiographic evidence of spondylosis present in the majority of individuals over 50 years 2
Clinical Implications of Causative Factors
Understanding the etiology helps predict clinical presentation:
- Asymptomatic radiographic changes are extremely common, with imaging abnormalities frequently present in individuals without symptoms 5, 2
- Symptomatic compression typically requires both degenerative changes AND congenital narrowing of the spinal canal to produce neurological symptoms 7, 2
- Progressive neurological deficits occur when osteophyte formation and disc bulging compromise neural structures, either through direct mechanical compression or secondary ischemic changes 3
Important Clinical Caveats
Several critical distinctions must be recognized:
- Degenerative spondylosis differs fundamentally from inflammatory spondyloarthropathies (ankylosing spondylitis), which have distinct genetic associations (HLA-B27), inflammatory mechanisms, and treatment approaches 5, 6
- Radiographic severity does not correlate with symptom severity, as many patients with advanced imaging findings remain asymptomatic while others with minimal changes experience significant pain 5, 2
- The natural history is variable, with most patients experiencing intermittent symptoms that respond to conservative management, while a minority develop progressive myelopathy requiring surgical intervention 1, 2