Hi @kdo0827
You might be able to do the Tai Chi. There is no floor work, no bending or getting into strange positions (like in yoga), it is just very gentle movement that is not at all stressful to the knees or the rest of the body. Here is a link to one of the Youtube videos that I sent to @lioness, https://www.youtube.com/watch?v=ZxcNBejxlzs just take a look at it and see what you think. I'm sure it will help relieve stress.

Here is a sitting Tai-Chi video you might also enjoy looking at, https://www.youtube.com/watch?v=WJP1pysakXQ.