Y can i play football with a torn meniscus?

i supposely torn my meniscus 4 years ago playing high school football..at least thats what the docs said.i recently played semi pro football again 2 months ago jus to see if i still got the game n me.i had no pain just a little soreness in my knees and i have a soft bump on the side of my knee that feels uncomfortable not hurt..hours and some times days after my games.i can cut hard n run a 4.5 40 without a brace or anything.can somebody help me figure out whats wrong with my knee because i feel like the docs r not tellin me the truth n my teammates told me i might have water that jus need to be drained from my knee