Swelling of the feet and ankles is a form of oedema, or swelling due to excess fluid in tissues; oedema of the feet and ankles has many potential causes.
Liquids tend to accumulate at the lowest point in the body due to gravity; since the feet and ankles are closest to the ground during standing or sitting, gravity often contributes to oedema of the feet.
Swelling in the ankles and feet can be also caused by high salt intake, sitting for long periods of time, trauma to the feet or ankles, drug use or kidney or liver problems.
Kidney disease, pregnancy and congestive heart failure increase the chances that a person will experience swollen feet and ankles.
Due to the varied causes, if you have oedema it is important to see a doctor for a diagnosis to rule out a serious underlying condition.
Treatment of swollen feet involves addressing the underlying cause; elevating the feet, consuming less salt and moving the muscles of the feet and ankles may help reduce swelling.