it could also be traumatic arthritis (a form of arthritis that occurs post injury).

Remeber- there are countless reasons some people need a chair so don't worry people with assue you are "different". In fact, many of your co-workers may be relieved to see the chair (as they will have an opportunity to sit for 5 minutes when you arent in it). If you dont want anyone to know about your MS diagnosis just inform your doctor that there is to be NO mention of that particular health issue. One of the good things about HIPPA is that physician offices allow you to restrict who gets what info :-)

BTW- sorry for your bum foot!