When imaging is actually useful

For most back pain, an X-ray or MRI does not help. Guidelines advise against routine imaging because it rarely changes treatment, it often finds changes that are normal for your age, and those findings can lead to worry, more tests and treatments that do not help. A scan is useful in specific situations: suspected serious causes, or when surgery or another procedure is being considered.

When a scan is the right call

• Red flags suggesting a serious cause: cauda equina syndrome, fracture, infection or cancer. See red flags.
• Suspected cauda equina syndrome: MRI is the reference test and is urgent.
• Before surgery or an injection, when the result would change what is done.¹
• Progressive weakness or other worsening nerve signs.

When it usually is not

NICE advises against offering imaging in non-specialist settings for low back pain with or without sciatica, unless the result is likely to change management.¹ The 2018 Lancet series lists imaging among the tests and treatments that are overused worldwide for back pain.²³

Why more scans are not better

A review of scans from 3,110 people without back pain found that changes often described as “degenerative” are common and increase with age:⁴

Finding	Age 20	Age 50	Age 80
Disc degeneration	37%	80%	96%
Disc bulge	30%	60%	84%
Disc protrusion	29%	36%	43%

A report that lists these can sound like a diagnosis even when it is just age. That can make people move less, worry more and look for treatment aimed at something that was never the problem. See how the spine changes with age and disc bulge versus herniation.

Red flags are judged together

Single red flags are weak on their own; combinations and clinical judgement matter more.⁵ For cauda equina syndrome, red flags were more specific than sensitive when compared with MRI, so their absence does not rule it out, but their presence needs urgent investigation.⁶

If you already have a report

• Ask whether the findings match your symptoms, for example leg pain in the area of the affected nerve.
• Remember that most findings are common in people without pain.
• Ask what would change if the scan were repeated. Usually nothing; people improve long before discs change.

Footnotes

1. Low back pain and sciatica in over 16s: assessment and management (NICE guideline NG59). 2026. ↩ ↩²

2. Prevention and treatment of low back pain: evidence, challenges, and promising directions. 2018. ↩

3. The Lancet Series call to action to reduce low value care for low back pain: an update. 2020. ↩

4. Systematic literature review of imaging features of spinal degeneration in asymptomatic populations. 2015. ↩

5. International framework for red flags for potential serious spinal pathologies. 2020. ↩

6. Diagnostic accuracy of red flags related to cauda equina syndrome compared with MRI: a systematic review. 2018. ↩