As a general guideline, degeneration of the cervical spine (neck) refers to three structures: the bones, the discs, and the joints. X-rays are usually used to make this diagnosis. First the doctor looks at the height of the disc space where the fusion took place. This measurement is compared to the height of discs that show no sign of degeneration.
If up to 25 percent of the disc height is lost, there's mild degeneration. A loss of up to half the disc height is considered moderate. Severe is shown by a loss of more than half the disc height.
A second measure of degeneration in the cervical spine is the presence of bone spurs called osteophytes. As the disc degenerates, the joints start to get pressed together. The joints start to get worn. The body responds by adding more bone around the joints. This can actually result in less movement at the joint.
The spine can get stuck in a position of too much flexion called kyphosis or too much extension called lordosis. The degree of these curves can also be graded as mild, moderate, or severe.