Hi there, i woke up and my left ankle was swollen, it is not painful or anything. it just feels firm. it has a slight throbbing sensation like a pulse. i haven't done anything strenuous, so i'm not sure whats wrong?

Swollen ankle: You might have strained it a day or two ago and not be aware. An insect bite could have happened. I would take an anti-inflammatory such as aspirin for a day or two. If it continues for a few days then go to your primary care physician. If the swelling proceeds up you leg, you develop other symptoms such as redness, pain, or fever, then you should go to the Emergency Department immediately.

Sleeping injury.: There is always the possibility that, while sleeping, your foot was put in a prolonged unnatural position and the result is seen as ankle edema. Give it a day or two and see if there is improvement. If not, have a specialist take a look at it.