Honestly, I have osteoarthritis in my right knee. Unit fitness guy wanted me to get a knee replacement when I was 32... I said no. My chief did get a total knee replacement at the end of his career and they let him stay in until his retirement. Civil service for 15 years and guard for 19. If you go through the MEB for osteoarthritis, you will be found unfit as it is a disqualifying condition. If you get medically retired (which with your years you should) you will be afforded the special provisions for reserve technicians (ART's (I believe ARTs fall under this at least) and Guard Techs) where you can apply for disability retirement from the civil service. The union rep I've spoken with hasn't seen someone get rejected when they apply for this as those special provisions protect us as being in the service is a part of our job description. I am not a FERS lawyer though, so verify what I am saying with one of them. I'm in the process of an MEB and am going to apply for FERS disability once I get the paperwork stating that I was medically retired or separated. I hope this helps.