Can you tell if it is reasonable to let the meniscus heal itself as skin tears will?

Usually won't heal: The meniscus is a 'shock absorber' made of cartilage that sits inside the knee. There is one on the inside and one on the outside of the knee. As opposed to your skin which has good blood supply to it, the meniscus has very poor blood supply. For this reason the meniscus usually does not heal. If you have a torn meniscus and pain you should see your local orthopedist to discuss options.