Low-Dose Radiotherapy for Painful Knee Osteoarthritis

Knee osteoarthritis is a common cause of chronic pain and difficulty with everyday activities, particularly in older adults. Some patients continue to experience clinically relevant knee pain despite medication, therapeutic exercise, physiotherapy, or other conservative treatments. This prospective, multicenter study will evaluate changes in pain, physical function, health-related quality of life, and safety after low-dose radiotherapy (LDRT) in adults aged 60 years or older with painful primary knee osteoarthritis. All participants will receive the same treatment, and there will be no control or sham-treatment group. Participants will receive one course of low-dose radiotherapy to the study knee, consisting of six fractions of 0.5 Gy, for a total dose of 3.0 Gy, administered twice weekly on nonconsecutive days over approximately 3 weeks. Clinical assessments will be performed before treatment and approximately 45 and 90 days after the last radiotherapy fraction. The main outcome is the change from baseline to Day 90 in average knee pain during the previous 7 days, measured on a 0-to-10 Numerical Rating Scale. The study hypothesis is that average knee pain will be lower at Day 90 than before treatment. Other outcomes include physical function, health-related quality of life, the participant\'s overall assessment of the affected knee, pain response, analgesic use, treatment completion, additional knee treatments, and adverse events.