I don't know the answer, but I have wondered this many times. I will be interested to see what others say.
I was diagnosed with costo while still working and I still have the films. and now convinced now that it was the hug instead.
I've had costo quite a few times. One way I tell is that in the affected area, the space between the ribs is very sore to the touch. I expect to see a big bruise but there isn't one.
Also, costo is in one or more very distinct spots. Move an inch or so left or right and it doesn't hurt.
ess
Here are a few links that explain Costochondritis, Tietze Syndrome, Chronic Costochondritis, and the MS Hug.
I also included a link that discusses other conditions related to having along with Chronic Costochondritis.
http://en.m.wikipedia.org/wiki/Costochondritis http://
en.m.wikipedia.org/wiki/Tietze_syndrome http://www.medicinenet.com/
script/main/mobileart.asp?articlekey=6171
http://chronicfatigue.about.com/od/whyfmscfsarelinked/a/costochondritis.htm
http://www.*************.com/multiple-sclerosis/c/67078/67113/ms-hug/