At 4 weeks, I was told specifically not to walk. And my PT would have been horrified if I was trying to walk on slopes. I was told not to be on my feet for more than 30 minutes, if it could be helped. At 4 weeks, I was working on straightening and bending. By 8 weeks, I was told I could walk without the cane and that I could spend more time on my feet. Now here is the big difference....at 4 weeks, my leg would swell up with very little activity and was stiff all the time. By 8 weeks, my leg would only swell a little bit and it took longer to swell, and it was stiff but would loosen up quicker. Between 8 weeks and 12 weeks, I was building up stamina, and I was beginning to go back to my normal routine. At 3 months, I wasn't planning my day around my knee anymore, although my knee wasn't 100%. My surgeon said that most people notice a big difference around 3 months (12 weeks). So heal the leg faster at the beginning and you will be able to do more later.
My tip for you is to sleep at night with your leg elevated. With my 2nd leg, this is what I have been doing, and I have experienced a lot less swelling overall and a lot less discomfort. With my 1st leg, I could never get comfortable those first few weeks. With my 2nd leg, I sleep in a recliner with a cushion and foam wedge (specifically made to elevate the leg-- my PT place ordered it for me) propping up my leg and elevating it all night long. I can do things this time around that I had trouble doing with the 1st leg-- like take naps on my side or on my stomach on the bed, even though I am only 2 weeks out. Control the swelling in the early weeks, and you progress faster overall.
You will have time to build stamina between 8 and 12 weeks.