knee meniscus tear

I had arthroscopy on both knee meniscus in the past. Now, MRI shows I have another tear in my left knee, where I already had an arthroscopy to remove a torn piece 8 years ago. There was some arthritis but not enough for replacement. I am 72.
I did 3 months of PT and it helped and I continued the exercises at home for the past 5 months. Now I am having pain in the knee again and due to have another cortisone injection. My question is : If i have another arthroscopy to remove tear...isn't that going to make it bone on bone real soon? I'm thinking why have that to relieve pain if it puts me down to bone on bone???