Joint bleeding is common in patients with hemophilia, most often in the knee, elbow and ankle joints. When blood pools in the joint cavity, it can restrict the movement of the joint and cause temporary loss of function, such as bleeding in the knee joint. It often takes several weeks for the blood to be absorbed into the joint cavity and gradually return to function, but repeated bleeding in the joint can lead to synovitis and arthritis, resulting in joint deformity and making it difficult to return the joint to normal function, so many hemophiliacs have varying degrees of disability. Hemophilia is a group of congenital coagulation factor deficiencies that lead to bleeding disorders. Congenital factor VIII deficiency is a typical sex-linked recessive inheritance, passed from female to male, and the gene controlling the synthesis of factor VIII clotting components is located on the X chromosome. When a normal male is married to a normal female, half of the children are normal males and half are transmitters; when a normal male is married to a transmitter female, half of the children are affected males and half are transmitters; when a affected male is married to a transmitter female, half of the children are hemophiliac boys and half of the children are hemophiliac girls and half are transmitters. Approximately 30% have no family history, and their onset may be due to genetic mutations. Factor IX deficiency is inherited in the same manner as hemophilia A, but in female transmitters, factor IX levels are lower and there is a tendency to bleed. Factor X1 deficiency all leads to impaired blood prothrombin formation, failure to convert prothrombin to thrombin, and failure to convert fibrinogen to fibrin, leading to bleeding.