Arthropathy is associated with the greatest cost and morbidity to persons with haemophilia. Clinical protocols have been developed empirically to prevent or retard the development of joint disease using routine infusions of replacement factor concentrate. However, randomized clinical trials to determine optimal therapy to prevent joint disease in persons with severe haemophilia are lacking. Two clinical trials are ongoing to answer important clinical questions about the prevention of arthropathy. The first, a US randomized clinical trial, is comparing an aggressive multiple-infusion episode-based protocol to standard alternate-day prophylaxis to determine whether prevention of joint disease requires prevention of the bleeding event, per se, or can be achieved by promoting complete resolution of each bleeding event in the joint. This study included the development and validation of sensitive new physical and imaging scales to detect the earliest signs of joint disease in young children. The second, a single-arm, open-label Canadian study, is asking whether prevention of joint disease in young children can be individualized by escalating the dose and frequency of routine replacement infusions of factor concentrate based upon the clinical course of haemophilia in the affected child. Both of these studies will contribute valuable information regarding optimal therapy and will help establish evidence-based medicine for the management of severe haemophilia.