Radiosynovectomy is known since 1952, since then a variety of different radiocolloids have been used. The aim of this study is to evaluate the role of radiosynovectomy using Yttrium-90 nanocolloid in local management of Rheumatoid arthritis involving knee joint. It is considered a pilot study conducted on eight patients with Rheumatoid arthritis of the knee joint, carried out at Kasr- El-Aini University Hospital from the period of September 2002 to August 2003 in Oncology and Nuclear Medicine Center. Patients were reviewed after 3 months duration after injecting 185 MBq of Yttrium-90 in the knee joint. The final results showed that 4 patients had good results and the other 4 patients had poor results.