It is not so rare. People with low thyroid can have this easily.

I'd suggest you try some magnesium lotion on your instep and ankles. This improves circulation quite a bit.

Also keep the feet up whenever possible. Watch your salt intake and MSG in processed foods. MSG is terrible for foot pain.

This is the lotion:
http://www.mortonsalt.com/for-your-h...-epsom-lotion/
Just apply about a quarter's diameter divided between the feet once a day.
WalMart stores have this in most of them now. Go online and search your zip code for the product on their website. If yours does not have it...ask the pharmacy to order it for you. My store carries this and has since it just came out a few months ago.
It is also on Amazon. Both places have it for a very low price.
You can also soak in epsom salts, and this works well too. But the lotion is much more convenient.

If you use blood pressure pills? What type do you take? ACE inhibitors may cause foot swelling. Also long term use of diuretics deplete magnesium.

The magnesium lotion gets into tissues where circulation is poor, and it really works well. I LOVE it !