AbstractBecause there is little available data to demonstrate whether demand therapy is adequate to prevent progression of hemophilic arthropathy, a cohort of 64 patients with severe Hemophilia A (Factor VIII level<1%) and no inhibitor were studied with respect to the progression of knee arthropathy over a period of 6 years. Both degree of disease in flexion and extension and progression of disease were rated on an arbitrary scale. At the outset of the study, the majority of knees were either not restricted or mildy restricted as to motion. Of those knees that were not restricted at the outset, 96% remained not restricted. Of the knees that were mildy restricted, only 58% remained stable or improved over the 6 years, and of the knees that were moderately to severely restricted, 75% improved or remained stable. It thus appears that a demand therapy program can maintain normal range of motion in a knee joint. However, if the patient's joint has progressed to mild disease, the ability to maintain or improve the joint with demand therapy appears to be decreased.