We retrospectively studied the files of 669 patients with musculoskeletal tumors treated with limb salvage and reconstruction using fixed-hinge knee megaprostheses. We used the KMFTR prosthesis from 1983 to 1989 in 126 patients, and the HMRS prosthesis thereafter in 543 patients because of the anatomical femoral stem with one lateral flange for improved stress-shielding, the new hinge design and new generation polyethylene placed centrally in the metallic hinge, and the improved function compared to the former prosthesis. Distal femoral reconstructions were done in 474, proximal tibia in 163, extrarticular knee joint in nine, and total femoral in 23 patients. At 10 and 20. years follow-up, survival to breakage was 95% and 85%, to aseptic loosening 94% and 82%, to infection 90% and 82%, and to polyethylene wear 95% and 37%. A statistically significant higher survival to breakage of the HMRS prostheses was observed. No statistical difference of survival to breakage regarding the site of reconstruction, aseptic loosening, infection, polyethylene wear and mean functional score between the two types of prostheses was observed.