I had both knees replaced on Dec.4 of this winter.  Had PT 3x weekly until the end of January.  Really got along real well and right now I feel like I'm just about totally back to normal---except no knee pain.  I'm 74 but was fairly active and still farm so that must help.  I wanted both done at the same time so I only had to put up with the pain once. LOL  I actually had both of mine done at the same time by the same Dr.  I got what they described as "Smart Knees" in that they have some type of sensor in them that relays the knee activity, stride length, angle of bending, speed, etc., to your smart phone and then it is relayed to the Dr's.  The Dr I had was the only one installing them so he did one knee and then did the second as soon as he finished the first.  Had them done at New Castle, Indiana hospital and this doctor group includes the Dr that developed the knee replacement (I was told)