Ugh...Ignorance is such an ugly thing!
I have complete empathy for where you are at here. I am in a little different position in that I am the boss, meaning I have a group of folks who works for me. During the last few weeks of getting this massive flare under control and getting diagnosed, I actually missed 19 days of work - just went back this week! I've been struggling to catch up with my employees, then on Wednesday, one of them actually had the audacity to compare her recent bout with the flu to the severity of my RA. I wanted to sock her in the face. I felt the same way when I read your post about these two yahoos at your work. Then I remembered something...
I was, once, one of those yahoos.
This probably wont be a popular answer, but being so new to RA, I think I have a slightly different perspective. It hit me as this idiot was telling me that she understood how bad my body hurt because she just had a case of the flu and she was sort of achy too, that she had zero clue how bad it was. Had she been a co-worker, I probably would have said "Are you freaking KIDDING me?" But because she works for me, I couldn't do that, and it forced me to stop and think. I remembered those times when my mom, also an RA fighter, would complain of aches and I would think "suck it UP already!!!!" This was my own mom, who I love dearly, but I just didn't get how bad it was. It took inheriting this darn disease to completely open my eyes.
So my approach with this gal at work was to ask what she knows about RA. As she described her flu (haha), it hit me that she really had no idea. I put myself out there and explained it the same way my 8 year old does to others - the auto immune cells in my body are confused - and shared how using the walker has been tough, etc. It seemed to sink in. Then I let her know that I DO know what the flu feels like - it sucks - but boy, I would take that over RA in a heartbeat! That one really hit home.
You have a couple of things going with these jokers at work. One - you are outperforming them with your body not at 100%. ROCK ON!!!! However this is going to automatically create animosity, even in the best of conditions. Two - you have a protected work environment that really isn't offering much protection in this regard. If it was me, I'd probably invite the know-it-all to lunch, find some little work related topic to ask her about (to stroke her ego) and then find a way to work in how thankful you are that your company is helping to deal with your disease. Then I'd ask what she knows about RA, and work in your story. It is amazing how, when people feel even a little important, they can become your advocate very quickly. As much as you may not want to, investing a 30 minute lunch in this gal may not just help with her, but bleed over onto others.
Or you can whack her with your cane. I love that one too
Take care and remember you are awesome, and bright, and wayyyyyy better than this dumb disease and the goofballs you'll encounter in life!!!