The pathophysiology of degenerative disease of the lumbar spine.

Degeneration starts in one joint and eventually involves all three joints of the three-joint-complex (one disc and two posterior joints) at an intervertebral level. Later, mechanical changes occur that affect the levels above and below and cause similar changes there. The result is multilevel lumbar spondylosis and stenosis. The spectrum of degenerative changes in a three-joint-complex progresses through three stages, which help to predict the outcome of different types of treatment.