This is a boot cast. It is on my right foot. It is on my right foot because I might have an Avulsion fracture of the fifth metatarsal. This does not make my foot happy.
Fractures of the fifth metatarsal, the long bone that runs along the outside of the foot, are evidently common. This bone is shaped differently than other metatarsals—it has a little protrusion that sticks out where the metatarsal meets the tarsal. An Avulsion fracture occurs right across this protrusion, as if the bone was trying to rid itself of this odd little bump.
Even though the X-rays didn't show a fracture, hairline cracks may have occurred. Time will tell. The boot cast, which will be my constant companion (except for sleeping and showering) for the next 7-10 days, is needed in case there is a crack. Not wearing it could lead to an actual fracture, and that means a much less comfortable cast.
Avulsion fractures apparently happen when the metatarsal is stressed, particularly when the foot is twisted inward. I stepped on a step wrong, and then the pain started.
Fortunately, there was Vicodin for sleeping last night, and today it's already better. The anti-inflammatory benefits of the way we've been eating have paid off in a big way—today, there is no swelling or redness at all. Hooray for anti-oxidents!
UPDATE 082509: Not broken, but possibly bruised. The boot cast will be coming off for longer periods of time over the next week. Best of all—no hard cast. Yay!