Hi,

Painless swelling of the feet and ankles is a common problem, particularly in older people. It may affect both legs and may include the calves or even the thighs. Because of the effect of gravity, swelling is particularly noticeable in these locations.

Foot, leg, and ankle swelling is common with the following situations:

Prolonged standing
Long airplane flights or automobile rides
Being overweight
Increased age

Swollen legs may be a sign of heart failure, kidney failure, or liver failure. In these conditions, there is too much fluid in the body.
Source - http://www.nlm.nih.gov/medlineplus/ency/article/003104.htm

You may consult your Physician for further evaluation .

As such ankle swelling can be due to effect of gravity , age especially since you are over weight .

But the diagnosis of the condition is important and to rule out any liver , kidney and cardiac disorder .

You may undergo precautionary LFT,RFT and an EKG before considering this swelling as benign .