It might be to do with how long the replacements last and how many you can have.

I don't know about hip replacements, but I have OA in my knee (brought on my a knee injury so fortunately the only place I have it) and I had surgery to clean it out, get rid of some floating bone fragments that sort of thing when I was 48.

Anyway, the consultant reckoned the only thing that would cure me completely was a full knee replacement, but they didn't like doing that on people under about 55 because the they only last about 15 years and the second replacement is reasonably straightforward, with the third replacement there is a 1 in 200 chance of losing your leg from the knee down.

So he reckoned it was best not to do it to younger people unless there was no other option.

This was private, I got BUPA from work then, so it wasn't an NHS thing saying you couldn't have it below 55.

The NHS wanted to send me to a Pain Management Clinic.