You have several options. Get a note from your doctor saying that you are unable to return to work until a certain date. Ask your employer if he could temporarily place you in a job you can do until you heal or allow you to work part-time in an easier job. If you are terminated, you probably can get unemployment, but you can't keep it if you take a job elsewhere. It's one or the other. Many people have knee replacements and Arthritis and are still able to work. Knee replacements heal and people do just fine with them. There is a normal healing time for most individuals, so if you have passed that time, you could be seen as playing the system. You'll have to choose what you want to do, but talking to your employer more about this situation might be the best thing you can do.