What Causes Swelling On Foot Top And Ankles?

i went to the dr. last month and explained my feet (tops) and ankles were constantly swollen, had bee since the first of year or so and were not getting better. They ran lab tests and said it was not sodium or other and that it wasnt kidneys by some number that returned w lab results, and that my heart sounds good. Im 59 1/2 and i wear a size 9 shoe most of the time. I recently had to buy size 11 clogs to fit my feet for work and ny socks always leave marks. They itch like crazy from skin stretched over the swelling i guess. What else could this be?