I tore my MPFL (Medial Patellofemoral Ligament) in Jan 2017. Had to wait 6 weeks to get surgery. Just as far as exercise goes, I lifted upper body all during the time before surgery with no issues (did walk with a cane for safety). Actually asked surgeon if I could play golf and if I could could hold the surgery off until fall… his words: “you can try”..with a laugh. I tried and could hit it ok but I knew it wasn’t going to work lol. But I digress….
I think I was back in the gym on crutches a couple days after my surgery. Possibly stoned on pain killers that first time as I just really really needed to get out of my parents house after laying on their couch for 2 days. but I could do some upper body stuff. Nothing crazy. It’s kind of a pain in the ass to go around on crutches, but you can get in there and do some arm work, machines, etc. Are you going to set any PRs..no, but you can get enough done that you’ll feel good. I’d be careful about any kind of chest press weather with significant weight because of the leverage you can use through your feet. Even leg stuff, you can do single leg leg press, extension, curl. There are studies that show that doing that single leg work with your good leg will benefit the side that is injured.
PT combined with that and my guess is you’ll be back to normal within a couple weeks of the doctor giving you the full go. Took me a while to get my full on leg strength back, and my injured leg will never get there..but I also had a pretty serious injury where my quad shut down. And most of my therapy was around getting that muscle to fire again. Wouldn’t think you’d have that with a meniscus. If you lift heavy normally, treat it as you giving your body a little break and reset.
I’m not an orthopedic surgeon, but I did stay in a Holiday Inn Express last night