Picture this: You’ve decided to change a lightbulb. You know, that one in the hallway that’s been flickering like a disco strobe since 1997. You climb the step stool, reach up, and suddenly gravity remembers it has a grudge against you. You land safely-ish, but your knee has decided to resign from its position as a functioning joint. You reach for your phone to call your daughter, but—plot twist—your phone is on the kitchen counter,…