Routine surgery found the partial cartilage tear that everyone had suspected and fixed it. Was up and about within 40 minutes of coming round from a general anaesthetic and home within a couple of hours. Delighted to report that the nausea I have experienced on previous occasions with generals was simply not there. I guess technology has moved on.
So thank for your prayers. My knee is a bit sore (but nothing like as bad as I expected) so I'll be resting it up for a few days within an exercise regime.