Authors of a recent paper from the Department of Anatomy at the Univeristy of Bristol (Canada) suggested the following definition as a place to start: An aberrant, cell-mediated response to structural failure. This means too much load on a disc can cause damage that starts a response at the cellular level. The result is even more disruption and damage to the disc.
In the normal, healthy adult, healing is initiated by the body in response to the damage that occurs. Factors that can disrupt healing include genetic or inherited tendencies, smoking or tobacco use, and physical load.
Physical loading refers to repetitive motions such as bending or twisting. Work- or job-related activities that involve bending or twisting while lifting are big risk factors for disc degeneration and damage.Many people start to develop disc problems in their 40s and 50s. You are only slightly outside the "normal" range for degenerative changes. Any of the risk factors mentioned could be contributing to an accelerated aging process.