Good news, my wife had knee replacement just over a year ago. A bit surprising that it is now basically outpatient surgery. She's just about fully recovered except for the occasional flashes she gets from a nerve or two. We did several longish walks/mini hikes while on vacation, including a few tough hills with no problems.
The only really scary part was when she fell in the bathroom the first night post surgury. She had the walker but just went down, nothing was damaged in the process outside of her pride. She had a minor tumble earlier in the evening which turned out to be instrumental in getting her back on her feet the second time. i was asleep and she didn't wake me til she fell.