With a degenerated disc, the proteins and cartilage of the disc change as it loses water. This causes the disc to lose its elasticity and ability to absorb shock. Because the disc is no longer cushioning the vertebrae around it, the bones above and below the disc feel more of the stress of movement. This can cause bone spurs and a condition called sclerosis. Both of these are visible on an X-ray.
Line Drawing Animated Video of Degenerative Disc Disease