This is the first RCT to examine the effectiveness of low-dose radiation therapy (LDRT) in patients with knee OA with the radiation dose, as recommended in the present guidelines. Elien A M Mahler et al. were not able to depict a substantial beneficial effect of LDRT on symptoms and inflammatory signs in knee OA when compared to sham treatment. They recommended against its use as a treatment for knee OA due to the absence of other high-level quality evidence favouring LDRT.

Low-dose radiation therapy (LDRT) for benign disorders example knee osteoarthritis (OA) is widely used in some parts of the world, despite the absence of controlled studies. The investigators evaluated the effect of LDRT on symptoms and inflammation in patients with knee OA.

This randomised, double-blinded, sham-controlled clinical trial (RCT) included the patients with knee OA (clinical ACR criteria) in the Netherlands. They aged ≥50 years, had a pain score ≥5/10 and did not respond to analgesics and exercise therapy. Patients were randomised 1:1 to obtain LDRT (1 Gray per fraction) or sham intervention six times in 2 weeks, distinguished by pain (<8 versus ≥8/10). Primary outcome included the proportion of OMERACT-OARSI responders, three months postintervention. The secondary outcomes comprised of pain, function and inflammatory signs examined by ultrasound, MRI and serum inflammatory markers.

Fifty-five patients: 27 (49%) to LDRT and 28 (51%) were randomly assigned to sham. At 3 months postintervention, 12/27 patients (44%; 95%  CI 26% to 63%) in the LDRT versus 12/28 patients (43%; 95%  CI 25% to 61%) in the sham group responded. The difference 2% (95% CI 25% to 28%) and the OR adjusted for the stratifying variable was 1.1 (95% CI 0.4 to 3.2). Also, there were no differences for clinical and any of the inflammatory signs.

There was no substantial beneficial effect on symptoms and inflammatory signs of LDRT in patients knee OA as compared with the sham treatment. Hence, based on this RCT and the absence of other high-quality evidence, they advise against the use of LDRT as a treatment for knee OA.