If both of your ankles are swollen, then it could be due to the amount of IV fluids .
If it is on the same foot that you have had the surgery, then it is normal. If any bone procedure was done to correct any deformity, you can think about it as being the same as if you broke a bone in your foot. Your foot and ankle will swell. With time is should go away. Let the surgeon know, elevate and ice.