Is it safe to kayak post hip replacement surgery?

Depends: White water, flat water, sea? Depends on type of kayaking. Standard flat water kayaking should be absolutely fine. White water and sea surf kayaking can be risky due to the potential need for rapid escape. Rolling the kayak would not be a major concern. A leg getting stuck in the kayak for a capsized escape is of concern.

Yes: In general it is possible to kayak post hip replacement, and, in fact, one of my patients has been a national kayaking champion for age/gender for a number of years. But it is important to be fit, keep the muscles strong, and in general, be knowledgeable about the sport, if you are planning to do this a high level. For recreational kayaking you should be fine. You should ask your surgeon as well.