Low-Dose Radiation Therapy (LDRT) Success Rates

Research on low-dose radiation therapy (LDRT) for osteoarthritis is mixed. Some older sham-controlled trials did not show a clear advantage over sham treatment, while a more recent randomized trial in mild-to-moderate knee osteoarthritis found improved pain and function at four months. Observational studies often report favorable results, but they are more vulnerable to placebo effects and differences in patient selection.

A National Consensus Guideline

In 2026, the American Radium Society published the first US multidisciplinary consensus guideline on LDRT for osteoarthritis, screening 548 articles and including 52 studies, 44 from that search and 8 found through citation searches. Across that body of evidence, the panel found overall treatment response rates of 60%-90%, with improvements in pain, joint mobility, and quality of life, and concluded LDRT is appropriate for selected patients who have not found adequate relief from conservative treatment.^[1] See our full summary of the guideline for how it was developed and what it recommends.

Positive Findings

A 2025 multicenter, randomized, sham-controlled trial (Seoul National University investigators, presented at ASTRO 2025 and published in BMC Medicine in 2026) enrolled 114 patients with knee osteoarthritis. At four months, 70.3% of the 3 Gy treatment group met the study's response criteria, compared with 41.7% of the sham group (p=0.021). No treatment-related toxicity was reported.^[2]

The ongoing US MOBILE observational study reported a 2025 interim analysis of 103 patients and 148 treated joint sites. Among the 76 sites with six-month follow-up, the average pain score fell from 7.6 before treatment to 3.4, and 84% of patients reported some pain improvement.^[3] As an observational study without a sham comparison, it can't isolate how much of that improvement came from the treatment itself versus other factors.

Mixed or Negative Findings

The German ArthroRad trial randomized patients to 3 Gy or 0.3 Gy. Both groups reported pain relief, but there was no statistically significant difference between the two doses at 12 months, and because the trial did not include a sham group, it could not determine how much of the improvement was caused by radiation rather than placebo or other effects.^[4]

A 2025 systematic review and meta-analysis pooling 12 studies and about 1,750 patients found no statistically significant benefit of LDRT over sham treatment for pain or physical function.^[5] A 2019 Dutch randomized, double-blinded, sham-controlled trial similarly found no substantial benefit for knee osteoarthritis symptoms or inflammatory signs.^[6]

How Long Does Relief Last?

Some observational studies and treatment centers report that relief may last many months and, in some responders, longer. Some programs consider retreatment if symptoms return, but policies vary by center.

A randomized study presented at ASTRO in September 2026 looked at much longer follow-up. It tracked 292 adults with early knee osteoarthritis (median age 38) for about 12 years. Patients who received LDRT plus glucosamine and chondroitin had more lasting improvement in pain and function than those on the supplements alone, less deterioration on MRI, and a 67% lower risk of knee-related disability. Among patients with grade 2 arthritis, disability developed in 31% after LDRT versus 61% without it.^[7] The study had no sham group, came from a single hospital in Russia, and used 4.5 Gy in 10 treatments rather than the usual 3 Gy in six, so the exact duration of benefit for a typical patient is still uncertain.

Summary

The 2025 Korean sham-controlled trial provides important positive evidence for a standard 3 Gy course, the MOBILE study provides encouraging real-world interim results, and a 2026 long-term study suggests benefits in early knee arthritis may last for years. At the same time, ArthroRad, the 2025 meta-analysis, and the Dutch sham-controlled trial show why the evidence should not be described as settled. The 2026 American Radium Society guideline weighed this same mixed body of evidence and still concluded that LDRT is appropriate for selected patients, which is meaningfully different from calling the treatment experimental or unproven. Differences in dose, patient selection, outcome measures, and follow-up length may contribute to the conflicting individual results, though that explanation hasn't been proven. A radiation oncologist can help interpret how these findings apply to a particular patient, joint, and treatment protocol.

References:
1. American Radium Society (ARS) Appropriate Use Criteria for Low-Dose Radiotherapy for Osteoarthritis. American Journal of Clinical Oncology, 2026 (ahead of print). View the publication 2. 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 Full results: Kim BH, Ro DH, Wang JH, et al. Single course low-dose radiation therapy in knee osteoarthritis (LoRD-KNeA): a randomized controlled trial. BMC Medicine. 2026. Article
3. Byrd HF, et al. Interim Analysis of Mitigating Osteoarthritis by Intervention with Low-Dose Irradiation to Extremities (MOBILE). ASTRO 2025 Annual Meeting, Abstract 249. Abstract
4. Niewald M, et al. ArthroRad trial: randomized multicenter single-blinded trial on the effect of low-dose radiotherapy for painful osteoarthritis. Strahlentherapie und Onkologie. 2023. PubMed
5. Hammadeh BM, et al. Efficacy, safety, and pain management of low-dose radiation therapy in osteoarthritis: a comprehensive systematic review and meta-analysis. 2025. PubMed
6. Mahler EAM, et al. Effectiveness of low-dose radiation therapy on symptoms in patients with knee osteoarthritis: a randomised, double-blinded, sham-controlled trial. 2019. PubMed
7. 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