I am not a doctor, so this represents my opinion and experience only.
The answer to your question is yes, you can use CBD and THC and stay active. It is really up to you and your tolerance as to how active you can remain while taking medical cannabis. I do not like to get high and I use CBD/THC everyday for pain and inflammation. I would recommend if you are sensitive to THC and do not want to get high that you try a high CBD product with moderate levels of THC and also use a topical cream.
You will need to experiment to see what works. My guess is is you have no knee cartilage that maybe swimming might be better though! 😉
I just wrote a new post on how to use cannabis without getting high:
Hope this helps!