It may not only be unhelpful to use X-rays, MRI and CT scans for people with low back pain, but it may also expose them to low doses of radiation unnecessarily.

When doctors do a physical exam of patients with low back pain and find no underlying cause, they sometimes order scans to check for problems such as broken bones or muscle injuries.

In this week's edition of the medical journal The Lancet, Dr. Roger Chou of Oregon Health and Science University in Portland and his colleagues reviewed six randomized controlled trials involving more than 1,800 people with low back pain who had either had the scans or didn't.

"Lumbar imaging for low-back pain without indications of serious underlying conditions does not improve clinical outcomes," the reviewers concluded, based on their assessment of pain, function and quality of life.

"Therefore, clinicians should refrain from routine, immediate lumbar imaging in patients with acute or subacute low-back pain and without features suggesting a serious underlying condition."

Rates of MRI scans for low back pain are increasing, and implementing guidelines on using diagnostic imaging for low back pain remains a challenge, the study's authors noted.

But doctors are more likely to follow the recommended guidelines now that there is evidence from higher quality clinic trials, they suggested.

"We need to identify back pain assessment and educational strategies that meet patient expectations and increase satisfaction, while avoiding unnecessary imaging."

In a commentary accompanying the study, Prof. Michael Kochen of the department of general practice at the University of Göttingen in Germany, agreed that patient expectations need to be addressed, since exposure to radiation doses from X-rays or CT scans is an issue.

But educating patients about the limited value of imaging did help reduce pressure to order imaging in one study.

Other factors, such as financial incentives for imaging and fear of missing problems are likely obstacles that prevent doctors from following the guidelines, Kochen added.