I experienced a meniscus tear from running some years back. While the medical people weren’t optimistic about my recovery, a trainer I went to was. It took some time, but I eventually got back to running (on a much more sensible basis) and along the way got serious about biking. At 72, I ride mostly gravel in hilly Vermont. With patience and work (and not too much pain), you can regain your fitness and meet your riding goals. Retirement is a great opportunity. Good luck!