That's how I think about my fall when I broke my arm. I had just the day before mentioned that I hadn't broken any bones since I was about 6. I realized I had jinxed myself, so I quickly knocked on wood. When I fell, I thought at first I had empirically proved that knocking on wood doesn't work.
But then I realized: I could easily have broken teeth, glasses, skull or neck but didn't (my son, watching from behind as I fell, thought I was going to break my neck; how scary for him!). And thanks to the broken arm, I got out of work for two weeks and out of working Saturdays for two months because I wasn't supposed to drive. My Saturday shifts at the paper didn't usually entail driving but required being able to at any moment, if needed. So I thought maybe the wood knocking did work, after all.
I'm all for wood knocking! I'm sure you can find scientific proof that it's working!

But from now on, I'll call it tur i oturen.
I'm very glad to be able to spread a bit of Swedish culture around here!

Yes, I've often heard that walking is really bad for you. 
People who say otherwise are definitely lying!
That of course doesn't include surgery, so I googled average cost of knee surgery: "The average cost for kneecap (patella) surgery in the United States can range significantly, but typically falls between $4,000 and $30,000 or more, depending on the specific procedure and many other factors. The total cost includes surgeon fees, anesthesia, hospital or surgical center charges, implant costs, and post-operative care like physical therapy."
My turn to say wow. I don't understand how Americans in general even cope with their lives. Everyone needs doctor visits or hospital care at least sometimes. How do people do it???