I have had two surgeries on my left knee, both out patient, both what they call twilight anesthesia. You're completely out, but you're not intubated.
The first was to repair torn miniscus, and a general clean up of the knee.
This was a piece of cake - had it done Friday, back to work Tuesday, gave up the crutches the second day. Did PT on my own, felt so much better after having it done, I was back to my usual routine, including riding, in a couple of weeks.
The second was something called a lateral release - they cut the patellar ligaments on one side of my knee cap to allow the knee cap to move over and level out, thereby alleviating much of the mechanical causes of the arthritis.
I think I took 3 or 4 days total off work for that one, straddling a weekend. That one felt terrific when it was first done, initial pain relief was great, and then I probably did way too much too soon; and the relapse was pretty awful. Ended up walking with a cane for a while. While I was back to my usual routine in about 6 weeks, it was about 9 months before I knew what I really had; and was happy I had it done.
On both of these surgeries, I was allowed to be weightbearing immediately, as much as I could tolerate.
Hope this helps, I have a thread about questions about partial or total knee replacement (that's where I'm heaed next) and there's a lot of great responses and info in that thread.