Within the knee occur 27.7% of all hemophilic bleeding episodes. Therefore it is the organ in which hemophilia is likely to be manifested. Changed in the sense of hemophilic arthropathy made 117 operative interventions necessary in the years 1973 through 1981. The osteotomies, performed to correct axial deviations (38 high tibial head osteotomies and 22 supracondylar osteotomies) formed the biggest group, followed by 34 hamstring-release operations, 6 synovectomies, 5 temporary epiphysiodeses, 4 ventralisations of the tibial tuberosis. An endoprosthetik replacement was necessary in only one case. A follow-up study after osteotomies and hamstring-release procedures after one to eight years, correspondingly six months to eight years, gives good results, concerning improved motility, subjective satisfaction and reestablishment of stabilizing muscular performance. In presence of sufficiently controlled substitution of the missing clotting factors, there is no increased operative risk, compared with non-hemophiliacs.