The parents of a 9-month boy bring the infant to the pediatrician’s office for evaluation of a swollen right knee and excessive bruising. The parents have noticed that the baby began having bruising about a month ago but thought the bruising was due to the child’s attempts to crawl. They became concerned when the baby woke up with a swollen knee. The infant is up to date on all immunizations has not had any medical problems since birth and has met all developmental milestones. Pre-natal, intra-natal, and post-natal history of mother noncontributory. Family history negative for any history of bleeding disorders or other major genetic diseases. Physical exam within normal limits except for obvious bruising on the extremities and right knee. The knee is swollen but no warmth appreciated. Range of motion of the knee limited due to the swelling. The pediatrician suspects the child has hemophilia and orders a full bleeding panel workup which confirms the diagnosis of hemophilia A.
Question: Briefly describe the pathophysiology of Hemophilia.