Low-Dose Radiation for Knee Osteoarthritis: The 2025 Trial

Short answer: A 2025 randomized trial found that six low-dose radiation treatments totaling 3 Gy improved a combined pain-and-function response at four months compared with sham treatment for selected people with mild-to-moderate knee osteoarthritis. The result is encouraging, but it is not a universal “70% pain relief” guarantee.

Why was a sham-controlled trial important?

Pain can change because of attention, expectations, natural fluctuation, medication, activity, or the treatment itself. In a sham-controlled study, participants go through the setup without receiving the therapeutic radiation dose. This helps separate a treatment effect from placebo response and normal symptom variation.

Earlier osteoarthritis radiation studies produced conflicting results. A well-designed sham comparison was therefore a priority.

How was the trial designed?

The multicenter Korean study enrolled 114 people with:

• primary knee osteoarthritis;
• Kellgren-Lawrence grade 2 or 3 changes on imaging; and
• substantial pain while walking.

Participants were randomly assigned to one of three groups:

1. 3 Gy total in six 0.5 Gy treatments;
2. 0.3 Gy total in six 0.05 Gy treatments; or
3. six sham treatment sessions.

Participants did not know which group they were in. Concomitant pain medication was restricted during the first four months except for rescue medication.

What did the study find?

At four months, the OMERACT-OARSI responder rate was:

• 70.3% in the 3 Gy group
• 58.3% in the 0.3 Gy group
• 41.7% in the sham group

The 3 Gy result was statistically significant compared with sham. The 0.3 Gy result was not.

A clinically meaningful improvement in the WOMAC total score occurred in 56.8% with 3 Gy and 30.6% with sham.

What did the trial not show?

Several secondary outcomes—including mean changes in visual pain score, patient global assessment, inflammatory blood markers, and rescue medication use—were not significantly different. No treatment-related toxicity was reported during the short follow-up.

The results were presented at a scientific meeting. At the time of this article, longer 12-month follow-up and imaging analyses were ongoing. A complete peer-reviewed publication may provide additional detail or change how the findings are interpreted.

Who was represented in the study?

The trial focused on mild-to-moderate knee osteoarthritis. It does not establish the same benefit for:

• end-stage “bone-on-bone” arthritis;
• hip, hand, foot, shoulder, or spine symptoms;
• rheumatoid or other inflammatory arthritis;
• people whose pain comes from another condition; or
• every age group and risk profile.

Accurate diagnosis and patient selection remain essential.

How low is 3 Gy?

The total dose was a small fraction of doses commonly used to treat cancer. The regimen was 0.5 Gy per session for six sessions. Lower dose does not mean zero risk, however. Radiation exposure should still be justified, planned carefully, and discussed in relation to age, pregnancy potential, prior radiation, and nearby organs.

How does this fit with other evidence?

The 2025 positive trial sits alongside older sham-controlled studies that did not find a meaningful advantage and a 2025 meta-analysis that concluded the evidence did not support routine use over sham treatment. Differences in dose, patient selection, joint, endpoints, and follow-up may partly explain the disagreement.

That is why this single study should update—not end—the evidence discussion.

Questions to ask before considering treatment

1. Is osteoarthritis confirmed as the source of my pain?
2. How severe is the joint damage?
3. Which standard treatments have I tried?
4. How closely do I match the trial population?
5. What benefit would count as meaningful for me?
6. What is known and uncertain about long-term risk?

The trial makes low-dose radiotherapy a more evidence-informed conversation for selected knee osteoarthritis patients. It does not make it the first or best option for everyone.

Questions patients often ask

What does a 70% response rate mean?

It means 70.3% met a predefined combined pain-and-function response at four months. It does not mean 70% became pain-free or that the benefit will last indefinitely.

Was the 2025 study peer reviewed?

The results cited here were presented at the 2025 ASTRO meeting. Conference results are important but less mature than a full peer-reviewed publication with complete long-term data.

Did the study prove low-dose radiation works for all arthritis?

No. It studied selected people with mild-to-moderate knee osteoarthritis. Results cannot automatically be applied to severe disease, other joints, inflammatory arthritis, or younger patients.

Sources and further reading

1. Clinical Effectiveness of Single Course Low-Dose Radiation Therapy in Knee Osteoarthritis. ASTRO Annual Meeting (2025).
2. Low-dose radiation therapy offers substantial relief to people with painful knee osteoarthritis. American Society for Radiation Oncology (2025).
3. Randomized Clinical Trial of Low-Dose Radiotherapy for Knee Osteoarthritis. ClinicalTrials.gov (2026).