Impact exercises, like running, jumping, and tennis are not recommended post TKR. You're correct, the TKR knee is not an anatomical match for a real knee. The TKR knee has no cushioning properties, and that's why impact exercises are not recommended.

As much as I'm sure you love it, I would stop playing tennis, doubles or otherwise. I had to give up running, but can do almost everything else in the gym that doesn't involve impact, and that's a lot.