I don't have any medical training, but I also have a fair amount of stupid knee experience from the last several years, so I can share with you some of what I have learned from my own experience. I started with a partially torn ACL and over the next couple years acquired tears to both the medial and lateral meniscus along with a couple other ligament and bone injuries. Knees are definitely not fun!
My medial meniscus was trimmed, and the lateral meniscus was repaired. You've probably already read this or heard it from a doctor, but a lot of structures inside the knee do not have a good blood supply, so they heal poorly. If you have a tear in the correct portion of your meniscus, and the doctors think that you have a decent chance of having it heal, they'll probably try to repair it (stich it closed). The other option is generally to remove the torn piece of cartilage, leaving as much of the remaining intact cartilage in place as is possible. Unfortunately, although the long term prognosis for a meniscus repair is better than the removal alternative, the rehabilitation is much more serious. For my repaired meniscus I was completely non-weight baring on the leg for 6 weeks after surgery. That means walking around on crutches, which when you're 215+ pounds and completely out of shape, is definitely not in the slightest bit fun. I don't remember the specific recovery time frame for trimming the meniscus (a partial menisectomy) but that will vary from surgeon to surgeon anyway. It's generally much shorter, which will also mean that you will have less muscle atrophy. However, having a partial or complete menisectomy also increases the speed of progression of degenerative arthritis in your joint, which if you are also struggling with weight problems can land a bunch of other joint issues in your lap in a short amount of time.
Your orthopedist may also suggest waiting on surgery. A lot of people get by with just a torn meniscus, although it more than likely won't heal on its own. If you don't have surgical treatment, they will almost certainly recommend physical therapy. In any case, as soon as your swelling is down and your doctor will clear it, I would definitely recommend starting to work on strengthening your quads and hamstrings (what torn meniscus PT usually focuses on). These muscles really take a hit during recovery from knee surgeries, but are super important for having a good post surgical outcome. If you think surgery is looking likely, but you still need to give your leg a rest for a while, if you can manage it I think working on arm strengthening would probably be helpful. If I could go back in time, I would definitely have done that before my first knee surgery...
There are a few leg specific exercises you can do that are fairly low stress... Once your doctor clears you to do them, adding them to your daily routine will likely help to decrease your joint pain, increase joint stability, and improve the chances of a successful outcome if you do end up going for surgery. Quad sets, or contracting the quadriceps and holding for a specific count... like 10 or whatever, and then releasing. Doing sets of those (generally 10 or so per set, repeated several times... I always do 3 sets of 10 at a go) will help keep the quads happy... But with swelling etc. sometimes the quads are also really hard to get to contract, and that again is where PT is helpful. They can use electrical stimulation or other techniques to get your muscles starting to work better again. Another knee pt exercise is to contract the muscle like a quad set, then keep your leg straight and raise in the air and slowly lower it. It gives your quads a decent enough workout, and again it would be an activity you can do off your feet, so it's less stressful on your knees.
I definitely wish you all the best luck with your knee; I am at about 6 months out from my last knee surgery and still trying to get in to the routine of regular exercise. If you have any other specific questions or find you need to vent more if your knee ends up making you want to scream in frustration (mine sure does!) feel free to message me.
torn meniscus
