My older brother had a knee replaced last year as an outpatient and was walking same day. He had in home exercise therapy for a week and after that he was getting around really well on THAT knee. He needs to get his other done as well. At least now he knows what to expect...
My wife's knee was replaced over 12 years ago. It was whole different recovery back then..
Glad it worked well for your friend! Nothing like being able to walk and not in pain..