Hi lph, I have had a lot of health problems over the past 8 years and Lupus has been suspected, although not yet diagnosed. It does however, run in my family and I'm on all the Lupus meds - so basically just waiting for a diagnosis really.
I am not sure whether your symptoms could be Lupus but I know the burning sensations in your legs was how my symptoms started 8 yrs ago. I too noticed it would be worse if i sat for long periods, especially at work. And like you said, it would be really bad that evening if I'd been sitting all day. I also noticed it would be worse when wearing high heels. I had trouble keeping my legs still as they would be so uncomfortable and my feet would feel like they were burning. It started in both legs and now is just in my left. It has however calmed down after several years and doesn't seem to bother me too much these days. The only time i notice it now is in winter when it is very cold (or when in an airconditioned room for long periods). I think this is called Raynauds Syndrome? I am unsure whether your hysterecomy is related, but my hormones seem to relate somehow to my symptoms as they are always worse when I am hormonal.
The only thing I can suggest to eleviate your symptoms is to try and steer clear of wearing high heels (if you do?!) and wear warm socks with covered shoes in cold whether or if working in an airconditioned office. This seems to have helped me. Hope this helps.