Pitting edema of only one lower extremity is a deep blood clot until proven otherwise. This is less likely in you because you have had two negative venous ultrasounds and blood clots usually don't cause pain in a joint. However, this does not completely exclude a blood clot. There could still be on that was missed by the ultrasound
, or it may be to high to be seen by the ultrasound probe. Assuming that the tests were correct and you do not have a blood clot, then we need to look at the other causes of edema in one leg. The ankle tenderness also changes the possibilities slightly. Any infection or trauma to the area can cause pitting edema. If the area of swelling and tenderness is also red and hot, then an infection in the soft tissue or joint must be excluded. Another cause of these symptoms is gout in the ankle joint. Gout can cause painful swelling of a joint that can look like an infection.
I suggest that you schedule an appointment with your primary care physician
. He or she can examine your ankle very closely and determine what is the most likely cause of your swelling (given the normal venous dopplers). Your doctor
may attempt to get some fluid out of your ankle joint for analysis or send you for an x-ray. Good luck.