I had some quite “unusual” meniscus damage. Walked out of hospital same day, signed off for 3 weeks. First week was mostly feet up (while the TdF was in the mountains, so that was okay). After two weeks I felt pretty much fine. Cycled again after about a month, just towpaths.
Knee was never 100% the same again, mind, but it’s doing really good now. A bit of singlespeeding and road riding seems to do it good – the former builds supporting muscles, the latter improved my pedalling no end.