Are they sure it's a meniscus tear? I feel your pain, literally. I'm 50, had arthroscopic surgery a little over 2 years ago, for a supposed meniscus tear (according to the MRI and my textbook symptoms), and once they got in there, all they found was chondromalacia. The doc "cleaned it up", and it was a long road back to running, which involved gait analysis, finding out all my biomechanical problems, getting rid of my orthotics and moving to more minimalist shoes, working on my weak hips, butt and feet. I finally got better and started racing again and ran well during indoor track last year. But, about 6 weeks ago I was out on a run, felt a sharp pain, had swelling again and instability just like the first time. After an MRI, the doc told me I have grade 4 arthritis under my patella and I will need a knee replacement eventually...in the meantime, I'm able to run, just not as much as I'd like to. I should probably try to cross train more but I can't get to a pool very easily to do deep water running. I do have a good stationary bike that I HATE riding but I will probably have to start using it more. I would also like to get a good rebounder and run on that some days. I have a cheap one and I actually kind of like using it.
I don't have any great advice. Some days are better than others. Make sure your glutes and hips are strong and have enough mobility. Work on your foot strength. I know my knee feels a lot better when I run lightly and make sure I don't overstride and heel strike. It actually feels best when I run totally barefoot on grass, but I can't really do that too often!! I started learning this new way to run by wearing Newtons at first and now I run in Altra's. I ice after almost all my runs, use a foam roller to keep my IT band in good shape, and continue to do all my hip and butt exercises. I take a few supplements in the hope they might help (Wobenzym, glucosamine and chondroitin, krill oil with hyaluronic acid in it too, and I think I'm going to add SAMe.) I don't know how helpful any of this would be for a torn meniscus, but I do know my husband who used to run mega mileage, once he tore his meniscus, developed arthritis too, so you sadly might be on the same path.