Radiotherapy 3 vs 6 Gy in Gonarthrosis and Coxarthrosis

This is a non-inferiority study in which the investigators compare two low-dose radiotherapy schemes, which are recommended from DEGRO Clinical Practice Guidelines (3 Gy vs 6 Gy) for the treatment of osteoarthritis and other osteodegenerative disorders. A first randomization will be carried out among the patients included in the study: * Patients in arm A will be treated at 3 Gy (0.5 Gy/fraction, 3 fractions/week), and patients in arm B will be treated at 6 Gy (1 Gy/fraction, 3 fractions/week). * Patients should not know the arm to which they have been randomized. * Once the treatment is finished, patients will be assessed at 8 weeks. If pain does not improve, a re-irradiation will be performed. If the patients were treated with 3 Gy a new randomization will be performed (3 vs 6 Gy again). If the patiens were treated with 6 Gy they will be re-irradiated with 6 Gy again. The investigators will analyze the results obtained depending on the dose received and depending on the location of the treatment.