It does depend on the underlying cause. Some PTTD is due to a traumatic injury or repeated microtrauma. More often than not it is due to structural abnormalities which makes both feet susceptible. My "good" foot started hurting a lot during recovery. My surgeon says that I have a high probability of that foot going bad, too. Overuse during recovery can stress even a strong foot, however. Suddenly the foot is handling twice the weight that it ever has so it's not unusual for it to protest. My doctor suggested I wear the ASO brace (that I wore pre-op with the bad foot) to help stabilize the good foot during recovery and that is what I did. Not all the time, but when it really started screaming at me. One thing about having this condition is that you know the signs and you know what you need to do to help the foot, unlike the first time when I didn't have a clue what was wrong with my foot. So you can do an earlier "intervention" and maybe prevent or at least delay surgery.

That being said, some people just never have a problem with the other foot, no matter the cause of the first one.