Again anecdotally, I have a keen running doctor friend in the UK who had 2 hip replacements by the time he was 40. Now that he's in his mid 50s, he's looking at replacements for his replacements.

Anecdotally. A friend is a surgeon. Does knees and hips. Says patients are getting younger. E.g. late 30s for total knee replacement is no longer uncommon; usually endurance athletes.