Questions about osteoarthritis.

I was diagnosed with osteoarthritis in 2009. I have a high tolerance for pain and waited until I was bone on bone and my leg was locking up before going back to the doctor. By the time I went to the doctor a TKR on my right knee was my only option.I have been out of work since April 29 and my surgery was May 14. I was put to the head of the line because my knee was a mess. This is my question about osteoarthritis. I have OA in my left knee as well. In fact it is slowing down the healing in my right knee because it is now hurting from being the weight bearing leg. The plan is to get the 3 injections in my left knee to help my right knee improve, but I know I am close to needing that one replaced as well.The surgeon said it was borderline. I also have osteoarthritis in my neck, spine, and shoulder and I have a herniated disc in my neck. I am 52 and I have a job that is physically demanding. Heavy lifting and on my feet all day. Because of this I am often in pain, which I tend to ignore, but am realizing I need to be listening to my body a little more. I do not think that I can do my active job anymore. I also can't sit at a desk for long periods of time. That hurts my lower back and sciatic nerve. I am at a crossroad here.At what point does it become a disability? I have the left knee that is going quickly downhill followed by my right shoulder. Has anyone had to make this decision and how did you know it was time?