No I haven't had a knee replacement but it is not a "stroll in the park " and it is a bigger deal than a hip replacement, a much bigger deal
You will have pain which will necessitate painkillers which is substantial initially but will eventually wear off over a period ranging from 2 - 6 months, each person responding individually.
You will need a fulltime carer when you get home.
Providing you exercise as directed, you will find the operation well worth while, but don't expect immediate results.