Hemosiderin deposition in hypertrophic synovium is a hallmark of progressive hemophilic arthropathy and accumulates with joint bleeding. . Conventional quantification of hemosiderin uses semi-quantitative MRI scores, assigning grades of small, moderate, or large to assess the burden of hemosiderin. To date, there is no known method to assess or quantify hemosiderin concentration within synovium due to the extremely short T2 values of this tissue. In this pilot study, we demonstrated that the clinically compatible IDEAL UTE-CS-QSM technique can be used to quantify hemosiderin depositions. We have shown that synovium in joints with hemophilic arthropathy demonstrates various susceptibility values, likely corresponding to different concentrations of hemosiderin.