The nucleus pulposus of the disc slowly degenerates during the first few years of life. It loses a high percentage of its water and may become partially calcified. Normal activity or minor trauma to the discs such as jumping, falling while playing, or running can initiate disc extrusion. When the disc extrudes, the nuclear content extrudes upward into the spinal canal. The compression collapses blood vessels and decreases circulation leading to deprivation of oxygen and glucose to the nervous tissue of the spinal cord.
Dysfunction follows in direct proportion to circulation disruption.
If the extrusion occurs during activity 5 the disc material may extrude with significant force - enough to cause impact injury in conjunction with the compression that follows.