Trauma, either single or repeated, is the most common mechanism of disc herniation caused by the rupture of the annulus fibrosus. This leads to the protrusion and/or extrusion of the disc material into the vertebral canal. When the disc has collapsed the space between the vertebrae is reduced.
Disc degeneration is often the result of life style activities, work related and tissue wear and tear. It usually arises in older people due to disc fibrosis and narrowing of the disc space, deterioration of the annulus, sclerosis of the vertebral endplates and presence of bony growths (osteophytes) in the inner space of the vertebrae. The prolapsed disc generates pressure to the nerves and possibly the spinal cord.