Repetitive stress injury and mice

I’ve been developing some pain in my mousing hand so I’ve been looking into repetitive stress injuries and ergonomic mice. The thing that is throwing me is that in every review I’ve read the reviewer states that the pain they are experiencing is primarily in the wrist, whereas my wrist doesn’t hurt at all, but my index, middle, and ring fingers are quite sore. Clenching my hand into a tight fist seems to alleviate the pain somewhat, as does using my gyroball exercise thingie. Anyone know what’s the story here?