When a person has spinal pain, plain film x-rays can be done that will show the outline of the bone and will detect the presence of bone spurs in facet joint disease. Discs, however, are made of soft tissue and are not detected on plain films. Plain films can, however, show narrowing of the disc space as is seen in degeneration of the discs.
A CT scan or MRI scan of the body can show a great many more things than a plain x-ray. These can show disc material impinging upon the spinal cord or on the spinal nerves. They can also show the presence of bone spurs at the level of the facet joints.