What Causes Lack Of Knee Pain If Having A Torn Meniscus?

About a month ago, I started having moderate knee pain. I went to a doctor, and I have 20% more fluid on my knee than I should and I also have a torn meniscus. I had an MRI done to confirm, and the Sports Medicine doctor I saw even believes that I have Juvenile osteoarthritis. I'm having surgery done tomorrow to repair all of the damage. The part I can't understand is that I'm not really experiencing pain anymore. What do you think? Is my meniscus not acually torn? Should I be concerned?