Thinking hard about this one, because in most cases, I simply have no choice. “Stay off it” sounds so simple. I even have crutches. But you can’t use crutches and carry things, so if I want to eat, I have to drop the crutches to carry my plate. If I want to feed my feline and chelonid “kids” I have to carry their dishes. If I want clean clothes, I have to carry the laundry. Having a cane or crutches, though, is a reminder for me. I may start to get up and then see the crutches and remember to grab them. I wonder, in your son’s case, though, if another solution might be better. What about talking to the doctor about having him use a walking boot for most or all of the day? That way he can actually walk on it safely. Normally they wouldn’t put you to that expense for less than a fracture, but the doc might consider it under the circumstances. Another possible solution that would be a lot cheaper would be to put something in his sock. That way, he’ll be bothered by that before he lands enough weight on the ankle to do any harm.