My ankles are okay except when they aren't. Every now & then (mostly if I'm carrying something heavy) one or the other will get a sudden very sharp pain and feel as if it's about to give way....but then it doesn't. I've sprained both anterior talofibular ligaments more times than I can remember, but never totally ruptured them the way I did my left ACL. Years ago, when I lived across the street from the U. of Wash. hospital, I had their sports medicine clinic tape the rt. one a couple of times a week until it was stable on its own. (The tape lasted through several showers). I do notice that both ankles swell considerably by the end of the day, but unlike after my RTKR, the calves and feet do not.
3 years ago I suffered a left 5th-metatarsal stress fracture on top of cuboid syndrome (that pesky hypermobile foot). It wasn't anything sudden, just cumulative long walks in Crocs (comfy for cooking or gardening but very little support or motion control, and the rubber soles can stick and make you move forward while your foot goes nowhere). My OS & podiatrist put me in a cast-boot for a month, and then I got orthotics. The cast-boot was fine and didn't really affect my gait because it had a rocker sole. Unfortunately, I'm between sizes and the M was too long and the S too small. We solved that with a semi-rigid OTC orthotic in the S extending far enough to support my toes without an abrupt hard edge. You really should have no problem with the boot, especially if you can wear a shoe with a similar sole profile and height on your other foot. (MBT or NB for casual and if you can afford it, Finn Comfort "Finnamic" for business or dress wear. For formal wear, just wear a normal shoe and milk that cast boot and its sympathy angle for all it's worth).