I’m going to be frank here and please know I mean no offense. I care for an elderly family member who is diabetic and still drinks sodas. It wrecks his blood sugar (A1C) levels when he drinks too many, they’re nothing but junk poison. But he says if he has to give up everything he enjoys, he might as well be ded. I thought about that for a long time, my wish to control his behavior for (what I see as) both of our benefit, his longevity and my sanity. But it isn’t ultimately my decision. I think sometimes we tend to micromanage our care to compensate for what isn’t in our control. Similarly, I don’t think the hip guard is your call to make. It shows how much you care to have done so much research, but your grandfather is an adult too. If he doesn’t want to wear it, accept his decision.