Unpredictable blood sugar will also be due to not moving around as much as usual. When I've had leg operations I have had really erratic readings for a few weeks after surgery due to all the above, inflammation, pain, stress and sitting down for a lot longer than normal. Walking on crutches I've found is a real glucose guzzler for the extra effort it takes even if you're partly weight bearing. Firefighting the highs is the safest approach when it's so unpredictable.
I hope your knee feels a whole lot better minus the staples and your recovery goes well. 🙂