Does a DEXA Scan Show Arthritis? What a Bone Density Scan Really Detects

Does a DEXA scan show arthritis?

No. A DEXA (also written DXA) scan is not designed to diagnose or detect arthritis — it measures bone density to assess osteoporosis and fracture risk. Arthritis is diagnosed by a different route: an X-ray, MRI or CT scan of the affected joint, alongside a clinical assessment by your doctor.

The organisation that sets the UK standard for bone health is explicit about this. The Royal Osteoporosis Society states that "a bone density scan is not done to provide information about cancer, pain or osteoarthritis" Royal Osteoporosis Society, 2024. So if your knees, hips or hands ache and you want to know whether it is arthritis, a bone density scan is not the test that will answer that question.

There is, however, a genuinely important twist — and it runs the other way. Arthritis does not show up on a DEXA scan as a diagnosis, but arthritis in your spine can quietly change the numbers a DEXA scan produces. That is the part worth understanding properly.

What is a DEXA scan actually for?

A DEXA scan measures your bone mineral density (BMD) — how much mineral is packed into your bones — to find out whether you have osteoporosis or are at risk of it. It uses very low-dose X-rays, usually scanning the lumbar spine and the hip, and the result is used to estimate your risk of a future fracture Oxford University Hospitals NHS FT, 2023.

Every part of that job is about bone strength. The scan is not built to image cartilage, joint spaces or inflammation — the things a doctor looks at to diagnose arthritis. If you want the fuller picture of what the scan reports, our guide to what a DEXA scan shows walks through the result in plain terms. The key point here is narrower: a DEXA scan answers "how dense are your bones?", not "do you have arthritis?".

Can arthritis affect the accuracy of my DEXA results?

Yes — and this is the important, well-evidenced part. Spinal osteoarthritis and degenerative change can falsely raise your lumbar spine BMD reading, making your bones look stronger than they really are. Osteoarthritic change adds extra dense material — osteophytes (bone spurs), facet-joint and vertebral end-plate sclerosis, disc-space narrowing and scoliosis — directly in the path of the X-ray beam, and the scanner counts that as bone.

This is one of the best-recognised sources of error in DEXA. A review of DXA artefacts notes that osteoarthritic and degenerative change is a known artifact that increases the measured BMD, and that guidance from the International Society for Clinical Densitometry (ISCD) is to exclude vertebrae affected by such artifact from the reading PMC6873828, 2019. The effect can be substantial: cited historical data referenced in one recent review suggest that even mild osteophytosis alone raised lumbar spine BMD by around 24% PMC10930380, 2024.

It matters because it can hide a real problem. In a 10-year study of 1,044 women aged 75, accounting for degenerative changes at the lumbar spine raised the measured prevalence of osteoporosis from 37% to 47% — degeneration had been masking osteoporosis in roughly one in ten of these women. The authors recommended reporting L1–L2 (the levels least affected by degeneration) when reassessing the spine Osteoporosis International, 2013.

Why does my spine result look better than my hip?

In older adults the lumbar spine is often the least reliable DEXA site, so a spine reading that looks noticeably better than the hip can be a red flag rather than good news. Osteophytes, facet-joint sclerosis, scoliosis, previous spinal surgery and calcification in the abdominal aorta can all spuriously elevate the spine number, while the hip (femoral neck) is usually far less affected.

Aortic calcification is a good example of how this happens. The abdominal aorta lies in the front-to-back path of a standard (anteroposterior) lumbar DEXA, so the beam detects calcium in the artery wall and adds it to the "bone" total. In one published case, an 89-year-old's AP lumbar spine scan read deceptively normal until a lateral DEXA — which excludes the aorta — unmasked severe osteoporosis PMC8282523, 2021. This kind of artefact is more common in the very elderly and in people with chronic kidney disease. It is one reason a clinician may weight the hip result, or discount an unexpectedly high spine number, in an older patient.

What do clinicians do when arthritis distorts the spine reading?

They don't take the inflated number at face value — international guidance is to exclude the vertebrae affected by artefact or local structural change, and to lean on a site that can be trusted. If too few evaluable vertebrae remain after exclusions, ISCD guidance is to base the diagnosis on another site, commonly the hip/femoral neck, or to estimate fracture risk with a tool such as FRAX rather than relying on the compromised spine PMC6873828, 2019.

Sometimes an additional view is used to see past the problem. As the aortic-calcification case above showed, a lateral DEXA that excludes the artefact can reveal the true bone density when the standard front-to-back view is misleading PMC8282523, 2021. The practical takeaway for you: if you have known spinal arthritis, it is worth asking whether your spine reading is reliable, and what your hip result says — because the two together tell a more honest story than a single flattering spine number.

Is radiation-free REMS less affected by arthritis than DEXA?

There is growing evidence that it may be — though this is still-emerging, and it should be read cautiously rather than treated as settled fact. REMS (radiofrequency echographic multispectrometry, a radiation-free ultrasound method) analyses raw ultrasound signals rather than an X-ray shadow, and researchers have suggested this makes it less distorted by the dense-material artefacts that inflate DEXA spine readings.

The signal from the studies points one way. In the 431-patient DEMETER study of people with lumbar-spine osteoarthritis, DEXA T-scores were significantly higher than REMS across every osteoarthritis severity grade, and REMS identified osteoporosis in 30.5% of spines compared with just 6.0% by DEXA PMC10930380, 2024. A smaller study of 159 postmenopausal women found the same pattern — among those with osteoarthritis, 35.1% were classed osteoporotic by REMS versus 9.3% by DEXA — and its authors concluded that REMS raw-signal analysis appears able to overcome common artefacts such as osteoarthritis and vertebral fracture PMC9118880, 2022.

That is promising, and it is a real difference in how the two technologies handle a degenerate spine. But detecting more osteoporosis is not the same as being proven more accurate against a gold standard in every case, so the honest framing is "emerging evidence", not "established superiority". Our REMS versus DEXA comparison sets out the trade-offs of each in more detail. Whichever scan you have, the result is best interpreted alongside your clinician's overall assessment.

The bottom line

A DEXA scan does not diagnose arthritis — X-rays, MRI/CT and a clinical assessment do that job. But arthritis matters for your bone scan in a way that is easy to miss: spinal osteoarthritis, osteophytes and aortic calcification can falsely raise the lumbar spine reading and hide osteoporosis, which is why clinicians may weight the hip or exclude the affected vertebrae in older patients. If you have known spinal arthritis and want a clear read on your bone strength, a proper bone health assessment interprets the numbers in context — and you can book a radiation-free bone health assessment to check where you stand.

---

This article is part of our screening technology series. To understand how radiation-free scanning compares with a standard bone scan, see our REMS vs DEXA scan guide.