Main causes for swelling over legs (including ankle) are renal (
kidney), cardiac (heart) and hepatic (
liver) disorders. As per your history it seems that you may have blood vessel related problem (eg. Peripheral vascular disease) for which doppler study of blood vessels of leg is required.
Other causes can be-
Anemia
Low
albumin
Hypothyroidism
Cellulitis
Next Steps
You need to consult a MS (General Surgery) or MD (General Medicine) doctor.