Sorry to hear that!!
I had my microfracture surgery 5.5 weeks ago (hopefully start putting weight on my left leg next Monday). Doc said once he got in there it was a lot worse than he thought...planed on 'tapping' 4 holes in my bone but ended up putting 7.
I've played tennis hard for 40 years (run everything down was always my motto). Avoided doubles because I didn't get a chance to run after everything and I had to think too much.
Doc says I shouldn't ever play tennis again (at first he said I could play doubles but now he advises against that).
Now I'm left searching for something to fill that competitive instinct. He advised cycling, which isn't bad, but I'm thinking table tennis.
Like you I expected to be out there when I was 75 beating 45 year olds in singles.
It's a tough pill to swallow...I feel your pain.
Enjoy each moment you're allowed to be on the tennis court!!!