I had a knee surgery a week ago. Prior to this I was following a semi-strict IF diet at a sustained -200 caloric deficit. Ever since the surgery, I've been eating more than usual, just said goodbye to my diet and eat, with my mind being to provide enough energy for the body to recover.

Is this the right way to approach it? If I go back to my old diet, but eat at maintenance level, will my recovery be slower?

Only old folk tell you after surgery need to avoid this and that. Doctor will say there is no restriction.

Just eat balance diet

Had the same situation as you, though my knee injury did not require surgery.
Eat for recovery and ditch your old diet. Yes, you will lose fitness and might gain weight. That's probably a given but make peace with it.

Once you are back on your feet and able to exercise, then go with a 60 day routine to shed that excess weight and up your fitness.
After that, you can probably go back to your old routine unelss you have special restrictions around that knee.

Diet should match your needs, not the other way round.

Yeah, I'm going down this route. Feeling a lot better. Thanks!

Speedy recovery!

A balanced diet is fine, but generally you would like to take more foods higher in protein for better recovery.