A common tool used to shrink cancer tumors may also change the course of knee osteoarthritis, not just calm the pain.
That is the takeaway from a new long-term analysis of a randomized trial in Russia, presented on September 27, 2026 at the American Society for Radiation Oncology annual meeting in Boston.
The trial followed 292 patients with early knee osteoarthritis for a median of 11.9 years.
People who received low-dose radiation on top of standard supplements had less structural damage on MRI, fewer disability claims, and, in the subgroup with more advanced disease, fewer knee replacements.
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What the trial actually did
Osteoarthritis is the wear-and-tear form of arthritis, in which the cartilage that cushions a joint gradually breaks down.
It affects an estimated 32.5 million US adults and is a leading cause of disability, according to The Osteoarthritis Action Alliance.
Many people still assume the damage is simply part of aging, even as researchers keep looking for treatments that go beyond pain management.
The Russian trial, conducted at a single institution, tested whether small doses of radiation could do more than dull symptoms.
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Patients had a median age of 38 and mild to moderate arthritis, graded 0 to 2 on the Kellgren-Lawrence scale used to score joint damage on X-ray.
Half received glucosamine and chondroitin, two commonly used joint supplements.
The other half received the same supplements plus a course of low-dose radiation, totaling 4.5 gray delivered in 10 sessions with an older orthovoltage X-ray machine.
A gray is the standard unit for a radiation dose.
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The published 10-year data appeared in the Bulletin of the Russian Military Medical Academy in 2025.
The follow-up analysis presented at the ASTRO meeting stretches to nearly 12 years and adds outcomes on disability and knee replacements.
The main findings
Across the whole trial, the radiation group had a 67 percent lower adjusted risk of being certified as disabled from knee osteoarthritis by government authorities.
MRI scans showed less deterioration inside the joint in the same group.
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Pain and physical function also stayed better over time, according to the ASTRO summary of the results.
The most striking numbers came from the subgroup with grade 2 disease, where cartilage damage is visible on X-ray but the joint is not yet severely worn.
In that group, 31 percent of people who received radiation went on to develop disability, compared with 61 percent of those on supplements alone.
And 14 percent needed a knee replacement, compared with 36 percent in the control group.
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Radiation for a non-cancer condition
Radiation used against cancer aims to destroy cells.
The doses tested here are much smaller and appear to work in a different way, by damping the low-grade inflammation inside the joint.
Koneru described the low-dose approach as reducing joint inflammation rather than killing tissue, according to the meeting press briefing.
Radiation for painful osteoarthritis is more established in parts of Europe than in the United States.
A recent European review noted that low-dose radiotherapy is used mainly for pain relief in older patients with hand and knee osteoarthritis, with symptom improvement in a majority of treated patients across mostly non-randomized studies.
Important limits
Patients knew whether they were receiving radiation, and the comparison group got pills rather than a sham radiation session, so a placebo effect on pain scores cannot be ruled out.
The trial was run at a single Russian center in a relatively young population, and the long-term analyses were exploratory.
The difference in knee replacements across the entire study population, as opposed to the grade 2 subgroup, did not reach statistical significance.
Long-term safety in younger patients also needs more study.
No new cancers or short-term radiation reactions were reported during the follow-up, but radiation carries a small theoretical risk of harm decades later, which matters more when a patient is treated at 38 than at 78.
Where this leaves patients
Low-dose radiation is not standard care for knee osteoarthritis in the US, and this trial does not change that.
Koneru said the next step should be a multicenter trial with sham radiation as the control, focused on patients with grade 2 disease.
For now, mainstream first-line options for knee arthritis still center on weight management, exercise programs and physical therapy, with medications and surgery reserved for more advanced disease.
Recent evidence has singled out structured aerobic training as one of the most effective non-drug options for chronic knee pain.
Anyone with persistent knee pain, morning stiffness or swelling should see a clinician for a proper diagnosis and staging before considering any treatment plan.
This article is made and published by Ida-Marie Palm Varbæk, who may have used AI in the preparation.