The doc that diagnosed the tear would be the best source for an opinion, especially if an arthroscopy was carried out, and it showed the true nature of the tear. ?small tear, ? big tear. ? loose piece, ? prone to locking the knee? etc, etc...
Generally, it would depend on whether or not it could interfere with the safe operation of the aircraft.
If you have a tear with a loose end which could get trapped and lock the knee on bending or straightening, you now have only one useful leg and possibly a lot of pain in the other. Not a good situation.
Now, if the tear is small and old and you have had it for eons without any problem then, maybe.
But again, somebody would need to assess your knee.