The present study was undertaken because we could not find references related to the minimal radiation doses emitted from patients treated with (90)Y-silicate colloid ((90)Y-SC) for radiosynectomy (RS). Radiation doses from 16 patients treated with about 181+/-13 MBq (90)Y-SC for RS of knee synovitis were estimated by dose rate measurements performed within 10 min after the (90)Y-SC injection with a calibrated survey dose ratemeter at 0.5 m, 1 m and 2 m distances from the treated joint. The mean dose rate values from the patients after bg subtraction were 0.6+/-0.4 microSv/h at 0.5 m, 0.1+/-0.1 microSv/h at 1 m and 0.1 +/- 0.0 microSv/h at 2 m distance. Dose rates at a distance of 0.5 m were significantly correlated (P<0.02) with the patient's weight but not with the height or the injected activity. The assumed estimated maximum whole body doses from a treated patient were 55 microSv for persons living with the patient, 2.9-3.4 microSv for the nursing staff, 0.2-1.8 microSv for the therapist physician and 0.3-0.6 microSv for the technologist, involved in the whole procedure. The above values were lower than those published with the same methodology for alternative RS radiopharmaceuticals for knee synovitis like dysprosium-165 ferric hydroxide macroaggregate ((165)Dy-FHMA) or holmium-166 ((166)Ho-FHMA), as estimated with their typical injected activities. In conclusion our results demonstrate that in (90)Y-SC knee synovectomy, the whole body radiation doses to medical and non medical personnel were as expected well below the maximum annual dose limits for the public and professionals exposed to radiation.