Aw, I'm sorry to hear that. AS can absolutely wreck your mobility over time. (And the reason I know is because I also have AS—I should've been more clear and gestured towards my username :P)
Not sure if it was the same thing, or just worn out hips, Osteoarthritis? But in retrospect, I've been thinking about it. A timer and getting up from the computer every half hour or wearing compression socks and maybe a foot massager would have helped. But I'm not sure if it would have been enough to prevent DVT.
HN doesn't have messaging features, does it? Feel free to shoot me a DM on Reddit then, I'm -ThisWasATriumph over there. (Just don't forget the leading hyphen in my username!)