There is confusion as to what constitutes degenerative disc changes from what normally occurs with aging. This often times leads to misinterpretation of normal intervertebral disc and spine aging as findings with degeneration. Fibrous tissue normally replaces the mucoid matrix of the nucleus pulposus over time with aging without leading to a loss of disc height. This is considered to be a non-pathologic aspect of aging that manifests as a small to moderate decrease in the signal intensity of the nucleus pulposus on T-2 weighted MRI images and should be uniformly present throughout the spine.
Intervertebral disc margins do not become irregular as a result of aging alone. Annular pathology, such as isolated radial fissures, are rarely present in those over the age of 40 as a part of normal aging. The presence of small amounts of intradiscal gas on imaging studies is not unusual for older individuals. Osteophytes involving the anterior and lateral margins of the vertebral body are considered a natural part of the aging process whereas the existence of posterior osteophytes and endplate erosions are considered to be degenerative.
Degenerative disc changes begin in response to repetitive micro trauma from eccentric or torsional loading producing early signs of mechanical failure. Tears involving the outer annulus within the region of disc innervation can produce back pain. Circumferential tears eventually coalesce and the nucleus pulposus loses its hydrophilic properties both of which lead to further disc degeneration.