Do we actually know the injury?
We know he had offseason surgery, and there aren't exactly many surgeries for severe knee bone on bone arthritis in people under 50.
A complete guess is he probably some mensical tears in there as well as some degenerative cartilage. They can just trim and suture the meniscus which is a 3 month recovery, but sometimes they drill holes in the cartilage to try and promote healing, or even try and graft a bit of good cartilage on. That's a much longer rehab timeline - 6 months plus. The research suggests return to sport rates are pretty good though.
I've had hope for Landry all offseason, but haven't had really much good news yet though.