Let me add further here.

X-Ray changes are non specific regarding the disc lesions. However, X-rays are usually required to rule out the other pathologies like fractures, mechanical derangements like Wikipedia reference-linkspondylolisthesis, spodylosis, spondlolysis, diffuse idiopathic skeletal hyperostosis (DISH), inflamatory arthropathies like Ankylosing spondylitis showing fusion of Wikipedia reference-linkSIJ, congenital anomalies like hemivertebra, spina bifida, measuring the degree of Wikipedia reference-linkscoliosis or kyphosis, watch the osteolytic or osteosclerotic lesion indicating bone tumours, vertebral collapse due to osteomyelitis, potts disease ( to assess the psoas abscess), etc.

Spinal X-Rays in a patient with back pain are required if the pain:

a- Start before the age of 20 and after 50 years
b- is persistent and a serious cause is suspected.
c- is worse in the night and in the morning, when an inflammatory arthritis(e.g. Ankylosing sponylitis), infection or a spinal tumour may be the cause.
d- is associated with a systemic illness, fever or weight loss
e- is associated with neurological symptoms and signs.

Spinal myelography, CT Scan both contrast or plain, Wikipedia reference-linkMRI of spinal provide better and detailed interpretation of soft tissue and bony tissue.

I think that it is sufficient to make the discussion more clear. Any more ideas are welcomed.