Suggest Treatment For Swollen Knees And Toes

I have suddenly got puffy knees and lately I have been to the docs telling her that i keep getting palpitaions she said if \I get the palpitations when I am resting it is better than when I am exercising are puffy knees related to it. I seem to be holding fluid quite a lot. I am an active 55 year old. 5'6 and 11 stone 4 doctor told me to cut down on caffeine which I have and only drink fruit teas etc. palpitaitons have stopped but have swollen kness and a little swollen just below my toes. Should I exercise more. What can I do., I feel I am active. I have an office job but never stop when I get home. I use to walk alot more but not done since my dog died. I was doing 3 mile a day. More like 3 mile a week now on top of what I do normally.