Low-Dose Radiation Therapy for Knee Osteoarthritis

Of all the joints treated with low-dose radiation therapy (LDRT), the knee has the most direct sham-controlled trial evidence behind it. LDRT is an outpatient treatment that aims a very small amount of radiation at the joint to calm inflammation in the joint lining.

What the Knee-Specific Evidence Shows

A multicenter, randomized, sham-controlled trial led by investigators at Seoul National University, presented at the ASTRO 2025 Annual Meeting and published in BMC Medicine in 2026, enrolled 114 patients specifically with knee osteoarthritis. Patients were assigned to 3 Gy in six fractions, 0.3 Gy in six fractions, or sham treatment. At four months, 70.3% of the 3 Gy group met the study's response criteria, compared with 41.7% of the sham group (p=0.021). The 0.3 Gy group was not significantly different from sham, and no treatment-related toxicity was reported.^[1]

A separate 2019 Dutch randomized, double-blinded, sham-controlled trial also looked specifically at knee osteoarthritis and found no substantial benefit for symptoms or inflammatory signs, a reminder that the evidence for the knee, while more direct than for other joints, is still mixed rather than settled.^[2]

The ongoing US MOBILE study (Mitigating Osteoarthritis by Intervention with Low-Dose Irradiation to Extremities) is a prospective observational study, not a randomized trial, covering knees and other treated joints. Its 2025 interim analysis included 103 patients and 148 treated joint sites; among the 76 sites with six-month follow-up, mean pain score decreased from 7.6 to 3.4, and 84% of patients reported some pain improvement.^[3]

Longer-term data are starting to appear. A study presented at ASTRO in September 2026 followed 292 younger adults (median age 38) with early knee osteoarthritis for about 12 years. Those who received LDRT along with glucosamine and chondroitin had more lasting improvement in pain and function, less joint deterioration on MRI, and a lower risk of disability than those who took the supplements alone. The study had no sham treatment, was done at one hospital in Russia, and used a different dose schedule (4.5 Gy in 10 treatments), so it needs to be repeated before the results can be relied on.^[4] Our article on the long-term study covers it in more detail.

Typical Schedule

• Total dose of about 3.0 Gy, split into 6 treatments of 0.5 Gy each
• Treatments given 2 to 3 times per week, over about 2 to 3 weeks
• Each visit takes roughly 10 to 15 minutes; no needle, sedation, or recovery period

Who May Be a Candidate

Programs generally consider adults with knee osteoarthritis who have not gotten enough relief from medications, injections, physical therapy, or other conservative treatments. The strongest recent sham-controlled evidence involved patients with mild-to-moderate knee osteoarthritis; patients with more advanced structural damage may be less likely to improve, since LDRT cannot regrow cartilage or restore a severely damaged joint. Many programs are cautious about using LDRT in younger adults, since radiation-related risk has more time to develop. A radiation oncologist weighs age, joint condition, prior treatment, and overall health together.

References:
1. 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
2. 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
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. 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