 Disc herniation is frequently associated with age-related degeneration of the outer ring, known as the "annulus fibrosus", but is normally triggered by trauma or straining by lifting or twisting.Tears are almost always postero-lateral (on the back of the sides) owing to the presence of the posterior longitudinal ligament in the spinal canal.A tear in the disc ring may result in the release of chemicals causing inflammation, which can result in severe pain even in the absence of nerve root compression.