What happens when someone with hemophilia is injured internally?

Anyone can start bleeding internally following a blow to the abdomen, head, arm or leg, or after a fall that injures the knee or elbow. People without hemophilia may stop bleeding and heal on their own. People with hemophilia may continue to bleed internally, slowly and steadily, sometimes for hours or even days after the injury. They may not even realize they are bleeding at first. But it is necessary to get medicine immediately. Why?

Let's look at an example. A joint is a place where two bones meet. Inside the joint is a space called the joint cavity. This cavity allows you to move the two bones. The bone ends that meet to form the joint are protected by a smooth substance called cartilage, which covers the end of each bone like a cap. 

Now let's imagine that someone with hemophilia falls and injures a knee. Blood steadily leaks into the joint cavity. The joint begins to swell and ache. The joint becomes stiff. The leg cannot bend, and walking becomes difficult and painful. Even worse, blood has substances in it called enzymes. Enzymes break down other substances. As blood accumulates in the joint cavity, enzymes begin to break down the blood to get it out of the joint where it does not belong, to be reabsorbed into the body. This is good. But as the enzymes do this, they also start to break down the cartilage covering the bone ends. If joint bleeds are allowed to continue for too long or happen too many times, the cartilage may become permanently rough and jagged, making smooth joint movement painful. 

Muscles are also a common spot for internal bleeds. Muscles can act like sponges, and can hold a lot of blood. Muscle bleeds cause swelling and can limit movement. Luckily, there are plenty of symptoms when someone gets a joint or muscle bleed: many say these bleeds feel "tingly," "funny" or "hot." Medicine (or clotting factor) can help stop a bleed before there is damage to the muscle.

Adapted from Tell Them the Facts! By Laureen A. Kelley, 1995