One of the best things to do after a total knee replacement is swimming. It's best to wait til the stitches or staples are out before doing so. The water helps support you and if you trip somehow, you're not going to fall face-first into a hard surface. The other good thing is that you don't need any kind of walking aids.
When I'm swimming, I don't just water walk. My therapist recommended walking forwards, backwards, and sideways, 3-4 laps each. I've also tried slow paddling for a minute or two, then return to walking. Leg lifts can easily be done as well. Don't just stay in the shallow end. I usually go from about 3 1/2 feet of water to 5 feet and back. Sometimes I'll stay in the 4.5-5 foot area for awhile. Maybe later I'll add on the flippers. Swim shoes seem to add a little more water resistance when slow paddling.
About 20-45 minutes of this could be the equivalent of an hour's worth of exercise without making you overly tired. Just make sure the water isn't too cold as it can make it harder to swim.
I still can't quite use the ladders, though I can still use the steps in the shallow end. If the pool is large and has steps in the deep end, I can use that.
Has anyone worn a wetsuit while doing their exercises in the pool?