Swollen Ankles

Hey everyone!

I have just started working (work placement/experience) in an accounting firm and it requires a lot of sitting. So, when I get home, my ankles are swollen and it only goes away when I do my workout, when I get home, and sometimes they are still a bit swollen after my workout.

My first question is - does anyone know what causes your ankles to swell? And secondly - how can I stop them from swelling?

Any help would be appreciated :)

Thanks