Are you saying you can't swim because of the knee or can't swim period?
You could swim without pushing off if it's the former.
I did the Atkins as well and the issue I had there is I felt like I was depriving myself because it was so restrictive. Same thing...when I stopped Atkins, I gained the weight back (eventually). The thing that's different to me for keto is I don't feel like I'm depriving myself. Because it includes oils and oils (well oils and sugar) are what makes many things taste good, the food is good and not like I'm restricting/depriving myself. Don't get me wrong, I'm not trying to convince you in any way, just saying why it's different/working for me.
I even made some home-made chocolate the other day for a treat. Unsweetened chocolate, raspberry extract, coconut oil, and swerve (mix of stevia and erithrotol if I recall) almost no carbs and satisfied the sweet tooth. I could also add nuts to it (one of the other things I like about keto...I LOVE nuts and I can have many different types). The
walmart market near us closed and I got a bunch of extracts for 50% off, so I can do orange, caramel, strawberry, coconut, etc..