I love this question. The research-tested answer is that routine imaging for patients with low pain is not warranted. In fact, routine x-rays are associated with increased cost, poorer health in recipients, increased risk of surgery, and no reduction in patient anxiety.
Imaging is needed if there are “red flags.” If cancer is a possibility, inability to control bowel or bladder functioning, fever, or severe neurological deficits.
X-rays should be performed if trial of therapy hasn’t worked, ankylosing spondylitis (an inflammatory problem) is suspected,or older patients with risk factors for a spinal fracture.
MRI imaging should be limited to patients with nerve pain or symptoms of spinal stenosis–when symptoms do not respond to therapy.
Dr. Leslie Greenberg's Blog 