What causes most of the pain when I have a stress reaction?

If you get a metatarsal stress fracture, the first thing that you're going to notice is not that you have a broken bone in your foot.  You are going to notice pain.  Typically, the feeling starts as a little vague discomfort in your foot that progressively gets worse as you continue to train and run on it.  The soreness gets worse the longer you run, feels worse when you walk barefoot on hard surfaces and becomes more notable going up and down wooden stairs.  As I explained this to a runner in the Injured Runners Aid Station, she asked "What really causes the pain?" What causes most of the pain when you have a metatarsal stress fracture?  Well, that's what we're talking about today on the Doc On The Run Podcast.