I am dreadfully nearsighted and have always had loose joints that dislocate easily, thus preventing me from running very well.

Pardon me for butting in here, but have your doctors ever discussed Ehlers-Danlos Syndrome (http://en.wikipedia.org/wiki/Ehlers–Danlos_syndrome) with you? It's what I've got, and it's incredibly common and incredibly under-diagnosed. Just from that sentence, it sounds like you might have it too!