Hey Mick,

I'm 68 y/o and had both knees replaced last year. I worked on my fitness for one year prior to surgery, and I'm a gym rat. That said, it's not uncommon for people like us, pushing 70, to get fatigued from the post-op exercises. I don't know your situation, but would venture that some tiredness is good, meaning that you are doing the rehab.

Joe