Low-dose radiation therapy (LDRT) for osteoarthritis is supported by over 80 years of clinical use in Europe, multiple randomized controlled trials, and a 2026 U.S. multispecialty Appropriate Use Criteria document. Overall treatment response rate: 60–90%. The randomized evidence divides by dose protocol: trials using the modern regimen (0.5 Gy per fraction, 3 Gy total) are positive; trials using the older higher-dose protocol (1 Gy per fraction, 6 Gy total) did not show benefit. Studies are presented below by protocol group.
Modern Protocol RCTs — 0.5 Gy/Fraction or Less
These trials used ≤0.5 Gy per fraction — the current standard in European and U.S. practice, endorsed by DEGRO and the ARS AUC. All are positive or show benefit.
LoRD-KNeA Trial (Kim BH, et al., BMC Medicine 2026) — 6 × 0.5 Gy = 3 Gy total vs. 0.3 Gy total vs. true sham (no radiotherapy). At 4 months, 70.3% responder rate in the 3 Gy arm vs. 41.7% sham (p = 0.021). Ultra-low-dose arm (0.3 Gy): 58.3% (p = 0.168, NS — directionally consistent with activity). The 3 Gy advantage held at 8 months but was not statistically significant at 12 months; secondary measures did not differ between groups. Read the paper
Fazilat-Panah et al. 2025 — 6 × 0.5 Gy = 3 Gy total vs. sham. Double-blind. All primary outcomes — pain, function, physical performance, analgesic use — improved significantly (all p<0.01), sustained through 6 months. View on PubMed
Makarova et al. (0.45 Gy/fraction, 4.5 Gy total) — 292 patients randomized. LDRT (0.45 Gy/fraction every 48 hours) + NSAIDs + SYSADOA vs. NSAIDs + SYSADOA alone. Both arms received identical background therapy — LDRT was the only difference. 9-year results: 67% arthroplasty risk reduction; 10-year results: radiographic progression 31.3% vs. 44.9%; marked deterioration 3% vs. 36.1%; disability 9.5% vs. 17.8%. MRI: preserved cartilage thickness, less bone marrow edema, decreased osteophyte formation.
ArthroRad Trial (Niewald et al., 2024) — Dose-comparison trial: 3.0 Gy (0.5 Gy/fraction) vs. 0.3 Gy (0.05 Gy/fraction); no true sham arm. ~60% improvement in both arms at 3 and 12 months. LoRD-KNeA data (showing the 0.3 Gy arm at 58.3% vs. 42% sham) is directionally consistent with activity of ultra-low doses — ArthroRad compared two active regimens. The open question is the minimum effective dose, not whether LDRT works.
Older Protocol RCTs — 1 Gy/Fraction (Both Null)
These trials used 1 Gy per fraction (6 Gy total) — approximately twice the current standard per-fraction dose. Neither showed significant benefit. The ARS AUC identifies the 1 Gy/fraction protocol as a specific methodological limitation that may have contributed to the null results. Additional factors: 55–56 patients (underpowered); 3 months follow-up only; refractory patient selection.
Mahler et al. 2018 — 6 × 1 Gy = 6 Gy total vs. sham. Knee OA, 55 patients. Responder rates 52% vs. 44% — not statistically significant.
Minten et al. 2018 — 6 × 1 Gy = 6 Gy total vs. sham. Hand OA, 56 patients. Responder rates 31% vs. 27% — not statistically significant. View on PubMed
van den Ende et al. 2020 (Lancet Rheumatology) — Long-term follow-up of the Mahler and Minten cohorts. Extended follow-up confirmed absence of significant benefit using the 1 Gy/fraction protocol.
Professional Consensus and Guidelines
ARS Appropriate Use Criteria (Dove A, Koneru B, Small W Jr, et al., 2026) — U.S. multispecialty committee (radiation oncology, rheumatology, orthopedic surgery, patient advocate) across seven institutions. RAND-UCLA Delphi methodology, 548 articles screened, 83 references. Overall treatment response rate: 60–90%. Read the full ARS Appropriate Use Criteria paper
DEGRO S2e Guideline (Mücke R, et al., 2022) — German national radiation oncology society guideline recommending LDRT for painful OA in appropriately selected patients. Foundation of over 80 years of routine clinical use across German centers. DEGRO Guidelines
International Benign Target Volume Group Consensus (Steike DR, et al., 2026) — 15 institutions across the U.S. and Europe standardized treatment volumes and delivery parameters for LDRT by joint type. Published in International Journal of Radiation Oncology, Biology, Physics. View Article (DOI)
Retrospective Series and Large Clinical Experience
Observational data from clinical practice. These series cannot isolate treatment effect from placebo response, but provide large-scale response data across hundreds to thousands of patients in routine clinical use.
Ojo et al. 2026 — Scripps Clinic, 184 joints (Advances in Radiation Oncology). At the first follow-up visit, 88% of treated joints had less pain; average pain fell from 6.3 to 2.5 out of 10. One of the largest single-center U.S. series to date.
Koneru et al. 2025 — U.S. series, 69 patients / 168 joints. 80% met the responder criterion at end of treatment; 72% remained responders at follow-up. Approximately one-third received a second course with additional benefit.
Koneru et al. 2024 — U.S. series, 51 patients / 85 joints. Foundational U.S. experience demonstrating feasibility and response rates consistent with European practice.
Mücke R, Seegenschmiedt MH, Heyd R, et al. Strahlenther Onkol. 2010;186:7–17 — Knee OA, 4,544 patients. 60% pain reduction at 3 months; 40% durable at 1 year. One of the largest published OA-LDRT datasets.
Donaubauer et al. — Hand OA, 483 patients. 70% pain improvement at 3 months.
Weissmann T, Rückert M, Zhou JG, et al. Front Immunol. 2021;12:777792 — Foot/ankle OA, 196 patients. 84% pain response at 3 months.
Alvarez et al. — Hand OA, 100 patients. VAS pain fell from 8 to 3–4 at 3–12 months; 70% functional improvement; no toxicity reported.
Hautmann MG, Hipp M, Neumaier U, et al. Strahlenther Onkol. 2020;196:569–575 — Ankle/tarsal, 66 joints. Median pain score fell from 7 before treatment to 4 at 12 months.
Trials Underway
Several new studies opened in 2025 and 2026. None has reported results yet. Two also test LDRT for arthritis that starts or flares during cancer immunotherapy, which is not the same as everyday osteoarthritis. Status as listed in October 2026.
Mayo Clinic (Rochester, MN): LDRT vs. steroid injection for hand and wrist osteoarthritis. Randomized trial comparing LDRT with a corticosteroid injection. 165 participants planned; recruiting since December 2025. Main outcome: hand pain. NCT07217405
Penn Medicine (Philadelphia): Prospective study of LDRT for osteoarthritis. Single-arm study tracking pain and function after LDRT for the hip, knee, hand, shoulder, ankle or elbow. 113 participants planned; recruiting since June 2026. NCT07715188
MD Anderson Cancer Center (Houston): PRAISE-BC: LDRT for immunotherapy-related arthritis in breast cancer. Tests whether LDRT to a joint that flared during immune checkpoint inhibitor treatment can prevent further flares and help patients continue immunotherapy. Funded in 2026 by an ASTRO-BCRF Emerging Investigator Award to Dr. Chidinma Anakwenze. ASTRO Foundation
University of Chicago: RADIATE: LDRT for arthritis caused by cancer immunotherapy. Early-phase safety and feasibility study in people whose arthritis began, or whose osteoarthritis flared, during immunotherapy; 20 participants planned; not yet recruiting. NCT07478679
See our full evidence page with detailed study summaries for each citation.
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Medically reviewed by:Robert Warren Floyd, M.D., Ph.D. — Resident Physician, Radiation Oncology, The University of Texas MD Anderson Cancer Center. Last reviewed: October 21, 2026. Independent personal project — not affiliated with or endorsed by MD Anderson Cancer Center. Funding & independence disclosure.
This content is for education only and is not medical advice. Always consult a qualified healthcare provider for diagnosis and treatment decisions.