that girl was on a BBC show about the human body and when it fucks up.
I think she has the same disorder that the guy in Mask had (not the Jim Carrey one, but the one with Cher).
Where the bone reacts to stress by quickly growing - so instead of a bruise, you get bone growth.
From what I have heard of it, it actually goes away in many people after they hit the age at which their bodies stop growing - then they can have surgery to correct it in many cases if not too severe.