Bleeding into the joints. This can cause swelling and pain or tightness in the joints; it often affects the knees, elbows, and ankles.
Hemophilia occurs in about 1 of every 5,000 male births. Based on recent study that used data collected on patients receiving care in federally funded hemophilia treatment centers during the period 2012-2018, about 20,000 as many as 33,000 males in the United States are living with the disorder. Hemophilia A is about four times as common as hemophilia B, and about half of those affected have the severe form. Hemophilia affects people from all racial and ethnic groups.
