Cannabis roots therapeutic?

I talked the other day to the husband of a medical marijuana patient who has fibromyalgia and finds cannabis gives her some relief, but he told me something I didn't know about that surprised me. He said there's a woman out there who asks people to send her cannabis roots -- any kind -- which she then grinds up and mixes into a salve. Given that THC is the major therapeutic agent in cannabis and the roots don't have any -- the only thing you'd get from smoking them would be a sore throat most likely -- you wouldn't expect it to work. But he said his wife tried it -- rubbed it onto especially painful places -- and found it worked very well, relieved the pain wonderfully. I haven't heard of this before, or heard of any tests done on such a salve. Does anybody else out there know anything about this? I'd be interested to find out. I thought I knew most everything a non-specialist could know about medical marijuana after writing the book, but this is a new one.

I'll be attending the Drug Policy Alliance conference in New Orleans in a couple of weeks, so I'll ask around.