I've read an estimate that, by age 70, 30% of the population will have had meniscus injuries and that most of them don't know it. If true, I guess that percentage would be a lot higher for tennis players.
I don't know if the meniscus sometimes heals or remodels (?) in some way. My meniscus tear from 2011 seems OK - no surgery, saw the Dr, got MRI, stopped tennis for 3 months and worked back into tennis slowly over two months.