Every company I have worked for has had policies on home medical leave is used.
- If you needed to miss a few hours (Dentist, Annual Physical...) no proof was needed.
- If you need to miss a day (Illness) you didn't need any proof.
- Needed to miss multiple day (3 or more) you might need to how you went to the doctor. This could for something like the flu, or even getting wisdom teeth removed.
- If you were going to miss longer, much more proof was needed.
For the longer duration they were concerned that employee who were sick for a week, were on vacation. In other cases we had a short term disability plan which covered your pay if you had to miss more than a week, or were admitted to a hospital. The paperwork for the short term disability was not trivial. The doctor need to provide a signed form with diagnoses, procedure information, dates and estimated time to return to work. The company had a medical staff to review the paperwork, before they would authorize payment for the missed days.
I am not saying your company does this, but they likely have some procedures in place to avoid fraudulent use of medical leave. HR will know. You should approach them early, the paperwork is much easier to process when you are not trying to do so while recovering from the surgery.