How does hemophilia affect bones?

Answer 1

It doesn't. It is a blood disorder. Usually occurs in males. They usually are missing a clotting factor - either factor VIII or IX. They have difficulty clotting their blood. They tend to have frequent bleeds and often these bleeds occur into their joints causing significant pain.

Here's a pretty good website with some basic info about the disorder.
http://www.umm.edu/altmed/ConsConditions/Hemophiliacc.html

Answer 2

I am WAY late to the party on this but I will answer anyway.

It actually DOES effect bones. The most common type of bleeding that Haemophiliacs suffer is internal bleeding into a joint (knees, ankles, elbows and hips being the most common). Regular bleeding into the same joint is very common.

Regular exposure to blood will eventually degrade the cartilage of the joint and cause pitting and roughness of the joint surface itself (i.e the bones). This results in pain and lack of mobility, even when there is no active bleeding taking place. Almost all Haemophiliacs over a certain age have at least one joint that is badly damaged and causes them pain and lack of mobility.

So, although Haemophilia does not directly affect bones, regular bleeding into joints caused by Haemophilia does.

Hope this helps.