There are two main types of haemophilia, classiied according to deiciency: type A, caused by factor VIII deiciency; and type B, which is rarer and the result of a deiciency in factor IX. Haemarthroses account for 80% of bleeding in haemophilic patients, with half of these exhibiting deformities. Repeated joint efusion leads to a local inlammatory response, with the formation of hyperplasic and hypertrophic cells and subsequent buildup of haemosiderin. Fibroblasts proliferate and produce collagenases and proteinases that act on the synovium, cartilage and bone, with a decrease in the joint space. Another mechanism involved is the damage caused by direct action of red blood cells on the cartilaginous surface of the joint lining. 153-samarium was obtained in research reactor by neutron irradiation of 152Sm 2 O 3 (99.4%) in the nitrate form, 152Sm(n,p)153Sm, for 30-36 h. The labelling process was performed with 40 mg of hydroxyapatite, according to Barboza et al. Radiochemical purity, particle size, microbiological tests for sterility and pyrogen were the tests applied to obtain an useful material. The introduction of 153Sm-HA for the treatment of haemophilic arthropathy in large and medium joints was a safe, cost-efective, minimally invasive and efective procedure in controlling bleeding and pain.