Imagine one day that your body start repairing microscopic tears in your muscles with bone. Grats! you have Fibrodysplasia ossificans progressiva or "stone man syndrome"
Pretty graphic images to some: consider that before clicking.
http://28.media.tumblr.com/tumblr_ll...ekz8o1_500.png
http://en.wikipedia.org/wiki/Fibrody...ns_progressiva