What causes spondylosis?

What Causes Spondylosis

Spondylosis is caused by age-related degenerative changes affecting the intervertebral discs and facet joints of the spine, representing a natural consequence of the aging process that is morphologically indistinguishable from senescent changes. 1

Primary Degenerative Mechanisms

The fundamental pathophysiology involves a cascade of structural deterioration:

• Intervertebral disc degeneration is the initiating factor, with progressive loss of disc height, hydration, and structural integrity 2, 1
• Facet joint degeneration occurs concurrently, with cartilage breakdown and subsequent arthropathy 1, 3
• Osteophyte formation develops at vertebral body margins and facet joints as a response to abnormal mechanical stress 2, 1
• Ligamentous changes including hypertrophy and calcification contribute to canal narrowing 1

Contributing Biomechanical Factors

The degenerative process is accelerated by mechanical stress patterns:

• Segmental instability develops as disc and facet degeneration progresses, leading to abnormal vertebral motion 3
• Malalignment can develop secondary to asymmetric degeneration, further concentrating mechanical forces 4
• Congenitally short pedicles or developmentally narrow spinal canals predispose to symptomatic compression even with mild degenerative changes 4, 5

Multifactorial Etiology

While aging is the primary driver, additional factors influence disease development:

• Genetic predisposition plays a role, though specific mechanisms remain incompletely understood 6
• Repetitive mechanical loading from occupational or athletic activities may accelerate degeneration 2
• Prior trauma including minor injuries can initiate or accelerate the degenerative cascade 4

Regional Variations

The cervical and lumbar spine show distinct patterns:

• Cervical spondylosis most commonly affects the C5-C6 and C6-C7 levels due to maximal mobility and mechanical stress at these segments 5, 2
• Lumbar spondylosis involves similar degenerative mechanisms but may progress to spondylolisthesis when facet orientation and disc degeneration permit anterior vertebral translation 6, 3

Clinical Significance of Degenerative Changes

A critical pitfall is assuming that radiographic spondylosis correlates with symptoms—spondylotic changes are commonly identified on imaging in asymptomatic individuals over 30 years of age. 7

• Symptomatic compression occurs when degenerative changes are superimposed on a developmentally narrow spinal canal 1
• Spondylotic myelopathy develops when osteophytes, disc herniations, and ligamentous hypertrophy collectively compromise the spinal cord through direct mechanical pressure or ischemic changes 4, 2
• Radiculopathy results from foraminal narrowing due to disc bulging, osteophytes, and facet hypertrophy compressing exiting nerve roots 4, 5

Natural History Phases

Degenerative spondylolisthesis follows a predictable progression:

• Dysfunction phase: Early disc and facet degeneration with preserved alignment 3
• Instability phase: Progressive segmental hypermobility with vertebral translation 3
• Restabilization phase: Eventual autofusion through extensive osteophyte formation and facet ankylosis 3