Hemophilia is a condition in which blood does not clot properly. What is the main effect of this condition?

decreased ability to heal blood vessel wounds

A blood clot stops the flow of blood from a damaged blood vessel. The vessels then undergo repair, and the wound heals. In hemophilia, the body loses the ability to form clots, which decreases the body's ability to heal wounds.

Your blood does not clot properly, because it lacks sufficient blood-clotting proteins.