Using radiation to treat an arthritic knee sounds unusual in the United States. Low-dose radiotherapy (LDRT), however, has a history of use for painful benign musculoskeletal conditions in parts of Europe and is now receiving renewed research attention for knee osteoarthritis.
The goal is not to destroy tissue. The doses being studied for osteoarthritis are much lower than typical total doses used in cancer radiotherapy and are intended to influence pain and inflammatory biology.
This page concerns native-knee osteoarthritis. If your knee has already been replaced and is painful, use the Pain After Knee Replacement pathway.
Compare knee arthritis treatment roles
What does treatment involve?
One regimen now being studied delivers a total dose of 3 Gray (Gy) as six treatments of 0.5 Gy, commonly given three times per week over about two weeks.
There is no incision, injection, or implant. Treatment is delivered by a radiation-therapy machine with the knee positioned in the treatment field.
The dose is low relative to common cancer-radiotherapy courses, but it is still ionizing radiation. "Low dose" should not be interpreted as "no risk."
What is it trying to change?
Low-dose radiation is being studied for anti-inflammatory and pain-modulating effects in arthritic tissue.
It does not:
- Restore a missing joint space.
- Correct bowleg or knock-knee alignment.
- Repair major instability.
- Replace damaged cartilage surfaces.
- Treat infection or another unexplained cause of knee pain.
The relevant clinical question is whether symptom improvement is large and durable enough to justify radiation exposure and the treatment burden.
Why is the evidence controversial?
Sham-controlled trials have not all reached the same conclusion.
A Dutch randomized double-blind sham-controlled trial enrolled 55 patients with symptomatic knee osteoarthritis that had not responded to analgesics and exercise therapy. Patients received six 1-Gy treatments or sham treatment. At three months, the response rate was essentially the same in both groups, and investigators found no substantial benefit in symptoms or inflammatory findings.
A newer multicenter Korean randomized sham-controlled trial enrolled 114 patients with mild-to-moderate knee osteoarthritis. Participants received sham treatment, a total dose of 0.3 Gy, or a total dose of 3 Gy in six fractions.
At four months:
- 70.3% of the 3-Gy group met the study's responder criteria.
- 41.7% of the sham group met responder criteria.
- The 0.3-Gy group did not significantly outperform sham.
- A clinically meaningful WOMAC improvement was also more common in the 3-Gy group.
- No treatment-related toxicity was reported during the short-term study period.
That is an important positive signal, but the report was short-term and long-term follow-up was still ongoing. Other secondary outcomes were not uniformly different between groups.
The most accurate conclusion is that modern low-dose protocols deserve further study, but one positive trial does not erase the earlier negative sham-controlled evidence.
What is happening in the United States?
A Mayo Clinic randomized sham-controlled trial has been studying low-dose radiotherapy for knee osteoarthritis in Rochester, Minnesota.
The ClinicalTrials.gov record last updated June 12, 2026 described a target enrollment of 128 participants and a 3-Gy regimen given as six 0.5-Gy treatments over two weeks, compared with identical sham treatment. The record still listed the study as recruiting and had no posted results at that update.
That matters because U.S. adoption should be interpreted in the context of an evidence base that is still being tested.
What about radiation risk?
The short-term treatment burden appears low in the available modern knee trials, but long-term risk is different from short-term side effects.
Ionizing radiation can theoretically contribute to later malignancy or other tissue effects. The absolute risk from a low-dose knee field is difficult to estimate precisely for an individual and depends on age, anatomy, dose, field, prior radiation exposure, and other factors.
That makes risk-benefit discussion especially important in a treatment for a noncancerous condition. A younger patient with decades of expected life ahead may view even a small theoretical late risk differently from an older patient with severe symptoms and limited options.
Who might discuss it?
At present, low-dose radiotherapy is most appropriately viewed as an emerging option for carefully selected patients with confirmed symptomatic osteoarthritis who understand the uncertainty.
It should not become a shortcut around basic diagnostic work or established treatment.
Reasonable questions include:
- Is knee osteoarthritis clearly the main source of my symptoms?
- What evidence supports the exact dose and regimen you use?
- Is treatment being offered as routine care, through a clinical trial, or through a registry?
- What short-term side effects do you see?
- How do you estimate long-term radiation risk for someone my age?
- What other nonoperative options remain reasonable?
- What will we do if the treatment does not help?
Availability
Low-dose radiotherapy for knee osteoarthritis is not yet a routine service across U.S. orthopedic or radiation-oncology practice.
Availability may be limited to selected centers, research programs, or clinicians with a specific benign-disease radiotherapy practice. Patients should verify whether a center is offering established clinical care, a clinical trial, or another research pathway.