Is joint effusion on MRI specific for haemophilia?

Magnetic resonance imaging (MRI) scores for haemophilic arthropathy are useful for evaluation of early and moderate arthropathy. The most recent additive International Prophylaxis Study Group (IPSG) MRI scale for haemophilic arthropathy includes joint effusion. However, it is unknown whether joint effusion is haemophilia specific. Correct interpretation of joint effusion is needed for outcome assessment of prophylactic therapies in haemophilia care. The aim of this study was to compare joint effusion on MRI between young adults with haemophilia and healthy controls. MRI's of both knees and ankles of 26 haemophilic patients (104 joints) and 30 healthy active men (120 joints) were assessed. Scans in both groups were performed in 2009/2010 and 2012 respectively. Joint effusion was measured and scored according to the MRI atlas referred by the IPSG MRI scale for haemophilic arthropathy. Median age of haemophilic patients and healthy controls was 21 and 24 years respectively. In haemophilic patients 23% of knees and 22% of ankles showed joint effusion. Healthy controls had significantly more positive scores for knee effusion (67%, P < 0.01) and a comparable scores for effusion in the ankle (17%). Joint effusion according to criteria of the IPSG MRI scale was observed significantly more often in knees of healthy controls, while findings in ankles were similar. These data suggest that joint effusion in knees and ankles is not haemophilia specific. Inclusion of joint effusion in the MRI scale is expected to reduce its specificity for haemophilic arthropathy.