Hello!

"Knee surgery" has a huge range from minor to major.

My most minor knee surgery I recovered within days and could do more exercise and a wider range of exercise as soon as the surgeon gave me the green flag (5 days post op). One leg deep squats, lunges, hopping and jumping around the Doctor's office convinced him I was already in a better place than before the op.

My most major surgery took over a year to rehab and although it vastly improved my situation the injury left me with some lifelong restrictions.

Gaining pounds of water weight after surgery can be totally normal as part of the healing process and doesn't need dieting to resolve (can also be counter-productive to diet while healing), have you got noticeable swelling?

What to eat depends on your goals and the severity of your procedure, if a significant surgery I would suggest eating at maintenance calories to support the healing process.

All exercise and general movement burns calories. What your capabilities are right now is completely unknown but hope you are getting some guidance from your medical team.