This paper reviews both the normal biomechanical behavior of the lumbar motion segment and changes in that behavior with disc degeneration. Each level of the spine consists of a disc anteriorly and two facet joints posteriorly. A complex ligamentous structure also contributes to the mechanics of the spine. Degenerative changes include intervertebral disc (nuclear) degeneration, facet joint osteoarthritis, vertebral body degeneration, and ligament degeneration. The goal of this review is to discuss the effect of disc degeneration on the biomechanical behavior of the spine, specifically the load-bearing and kinematic behavior after degeneration.