My friend used to be a track and field athlete. He has undergone hip resurfacing surgery. It has been 6 months. He has recovered very quickly and has returned to normal activities. Soon there is a marathon for public health. I wonder if he can join with that condition? Does he have to restrict anything?
Maybe. How is that for an answer?
Did he run marathons preop? Did he run any long distances? How much is he running now?
Honestly, I think to go from resurf to marathon in a year would be pretty aggressive. To a 10K? Probably fine. To a half? Maybe if he is young and was in good shape pre op. A marathon? I worry he would be pushing it too much, particularly if he lost fitness during the time period when his arthritis was bad.
FWIW, I was 53 when I got two new hips. I had been running 4-5 marathons a year until age fifty, then was laid low by arthritis. I built back to a 10K by my new hip anniversary and that felt about right. Your friend's experience may be different, but I'd say 5k-21K is probably a good range for year one.
For the second year? He can go for it!