Long-Term Study Suggests LDRT May Slow Early Knee Arthritis

Most studies of low-dose radiation therapy (LDRT) for arthritis follow people for a few months and check whether their pain improved. A study presented at the American Society for Radiation Oncology (ASTRO) annual meeting in late September 2026 followed people with early knee osteoarthritis for about 12 years, and it also looked at what happened inside the joint^[1][3].

What the Study Did

The researchers enrolled 292 adults with painful knee osteoarthritis at an early stage, Kellgren-Lawrence grade 0, 1, or 2 on X-ray. Their median age was 38^[1][2]. All of them were treated at one hospital in Russia. One group took glucosamine and chondroitin supplements alone. The other group took the same supplements and also had LDRT, 4.5 Gy given over 10 treatments^[1]. Patients were assigned to each group at random and followed for a median of 11.9 years^[2].

What It Found

• Pain and function: the LDRT group had more lasting improvement in pain, physical function, and quality of life than the supplement-only group^[1].
• The joint itself: MRI scans showed less structural deterioration inside the knee in the LDRT group. Their scores improved at 12 months, while the supplement-only group got worse^[1][2].
• Disability: after adjusting for other factors, the LDRT group had a 67% lower risk of becoming disabled by knee osteoarthritis over the follow-up period^[2].
• Grade 2 knees: the clearest difference was in the 78 patients whose arthritis was established but not yet advanced. Disability developed in 31% of those who had LDRT, compared with 61% of those on supplements alone^[1]. Knee replacement surgery was needed in 14% versus 36%^[2].

The MRI results stand out. Pain can improve for many reasons, including the placebo effect, but a difference you can see inside the joint on a scan is harder to explain away. It raises the possibility that LDRT slows the disease in some people instead of only easing the pain.

What It Can't Tell Us Yet

But the study has limits:

• No sham treatment. The comparison group took supplements only. Nobody received a fake radiation treatment, so the placebo effect could still account for part of the difference in pain.
• One hospital. Everyone was treated at the same center. Other teams will need to get similar results before doctors can rely on them.
• Younger patients with earlier disease. The median age was 38, and no one had advanced arthritis. Most people treated with LDRT are older adults, so the results may not carry over. Radiation programs are also more cautious with younger adults, since any radiation-related risk has more years to develop. See Can LDRT Cause Cancer? for the numbers.
• A different schedule. The study used 4.5 Gy in 10 treatments. The regimen most U.S. programs follow, supported by the American Radium Society guideline, is 3 Gy in six treatments^[7].
• Not yet a full paper. So far the results have only been presented at a meeting, as a short abstract. A full journal article would give other experts much more detail to check.

How It Fits With Other Research

The evidence on LDRT for knee arthritis is still mixed. A 2025 Korean trial that did use a sham treatment found that 70.3% of patients given 3 Gy improved at four months, compared with 41.7% after sham^[4]. A 2019 Dutch sham-controlled trial found no meaningful benefit^[5], and a 2025 review that pooled 12 studies found no significant benefit over sham for pain or function^[6].

The 2026 American Radium Society guideline weighed this mixed evidence and concluded that LDRT is an appropriate option for selected patients who have not done well with standard care. It does not recommend LDRT as a first treatment^[7]. What the new study adds is long-term follow-up and MRI results, which the earlier trials didn't have. On its own, it doesn't settle the question. Our Research and Evidence page lists all of these studies in one place.

What This Means If Your Knees Hurt

If you have early or moderate knee arthritis and your pain has not improved with exercise, weight management, medicines, or injections, this study is a reasonable thing to bring up with your doctor or a radiation oncologist. Ask whether your stage of arthritis is a good fit, what dose and schedule they use, and what results they have seen. Our guide on how to talk to your doctor about LDRT can help you prepare.

References:
1. Low-dose radiation therapy may slow progression of knee osteoarthritis, long-term study indicates. American Society for Radiation Oncology (ASTRO) news release, 2026 Annual Meeting, September 2026. ASTRO
2. ASTRO: Low-dose RT tied to fewer knee replacements. AuntMinnie, ASTRO 2026 conference coverage. AuntMinnie
3. Low-Dose Radiation Could Help Slow Knee Arthritis. HealthDay via U.S. News & World Report, September 30, 2026. U.S. News
4. Kim BH, et al. Clinical Effectiveness of Single Course Low-Dose Radiation Therapy in Knee Osteoarthritis: Short-term Results from the Randomized, Sham-Controlled Trial. ASTRO 67th Annual Meeting Late-Breaking Abstract LBA 06. 2025. Abstract
5. Mahler EAM, et al. Effectiveness of low-dose radiation therapy on symptoms in patients with knee osteoarthritis: a randomised, double-blinded, sham-controlled trial. Annals of the Rheumatic Diseases. 2019. PubMed
6. Hammadeh BM, et al. Efficacy, safety, and pain management of low-dose radiation therapy in osteoarthritis: a comprehensive systematic review and meta-analysis. Rheumatology International. 2025;45:210. PubMed
7. Dove A, et al. American Radium Society (ARS) Appropriate Use Criteria (AUC) for Low-Dose Radiotherapy for Treatment of Osteoarthritis. American Journal of Clinical Oncology. Published online May 25, 2026, ahead of print. PubMed