I worked in kitchens and as a server pretty regularly from about ages 16 to 22. After several back-to-back busy shifts my joints would hurt until I got a day off. Even at 36 now as I start to feel stuff ache a little more often and a little more acutely, it was different then. It's easy to see how decades of that kind of work can really take a toll on your body.
People who have never worked in a busy restaurant probably underestimate the type of toll that work takes on your body. It can be grueling.