Would you deliver low dose radiotherapy to a patient with persistent knee pain after knee replacement?

In general, I am pretty liberal about trying low-dose radiotherapy for osteoarthritis because it is so very low risk. In the case of pain after total knee arthroplasty, I am pretty sure all the studies excluded these patients. They excluded them because many/all of the structures that house inflammatory cells have been removed. I was able to find one ACRO abstract from this year (2026) that suggested that patients can have decreased pain with low-dose radiation (3 Gy/6 fx). The author hinted that perhaps the synovium and adjacent bone may house inflammatory cells that perseverate inflammation and pain. Although quantitative data were not reported in the abstract, it was suggested that this reduced pain and improved osteoarthritis assessment...

I have treated a few patients post-knee replacement (TKA). First, it's important to understand that persistent knee pain should prompt a careful evaluation to exclude periprosthetic joint infection, prosthetic loosening, instability, malalignment, and other correctable mechanical causes, with an effort to identify the specific pain generator. TKA itself should not necessarily preclude consideration of LDRT.

If the identified pain generator is inflammatory, LDRT may be considered. Persistent synovial inflammation, as well as periarticular tendinopathy, enthesopathy, or bursitis, may represent plausible radiation-responsive pain generators.

I would not offer low-dose radiotherapy (LDRT) for persistent pain after total knee replacement, as the etiology is usually different (issues with arthrosis, neuropathic, or fibrosis, and not inflammation).