BLEEDING RISK AND HEMATOMAS People with hemophilia have the additional risk of bleeding, which must be controlled during and after the procedure. Excess bleeding after surgery may lead to the development of a hematoma. A hematoma is a collection of blood under the skin causing swelling. Large hematomas may need to be aspirated or surgically drained. Prevention and control of bleeding risk for people with inhibitors usually means a bypassing agent will be prescribed. Your hematologist will monitor your condition closely to try to prevent and control bleeding during and after surgery. BLOOD CLOTS (THROMBOSIS) Blood clots in the veins are a complication of joint replacement surgery in people without hemophilia. In people with hemophilia A or B with an inhibitor, this is quite rare, but it may occur. Blood clots may be a particular problem in knee replacement surgery, and your doctors may recommend a prevention program. This may include periodic elevation of your legs, lower leg exercises to increase circulation, support stockings, and medication to thin your blood if necessary.