I have an meniscal tear,shud i exercise?

I have the same problem as you and my physiotherapist told me that I have to keep the muscles in my legs strong to avoid exertion on the knees. The stationary bike and cross trainer are good to strengthen the quadiceps, but put it on a very low level. Avoid any exercises that involve twisting, jumping or running. Make sure your calfs and hamstrings don't get tight, you can stretch them by putting a book against a wall and under your toes and lean forwards against the wall. Using heat will help blood supply which will in turn help the healing process, or use ice if your knee gets swollen.