HI! I'm glad to see you made your way here :-)
You know, I think it might be possible your left knee might be hurting because you're favoring your right knee. After my surgery in January, I developed horrible pain in my left knee and hip, and it was because of the way I was walking to compensate the knee pain in my right knee.
The doctors told me I do have arthritis in both knees, and I guess an injury such as yours could make it such that arthritis would develop in your knee... the grinding could be part of that. I take glucosamine, too, and I think it does help. I used a recumbent bike for awhile a couple of months after surgery, and that helped, too.
Anyway, it's good to have you here!