Depends upon what your symptoms are. If you are having episodes of true locking, then you have a mechanical problem and the cortisone will not do anything. If all you have is discomfort, then you might want to try the steroids to see if they help. They may make the knee more comfortable.
However, once a meniscus has a tear in the avascular zone, it cannot heal. But, that does not mean that it has to have an operation either. The indication for surgery is failure of nonoperative treatment methods.
You should really discuss your options with your orthopedic surgeon, as he/she knows your examination and results of any studies.