About the data: We used the family income data from the 2013 American Community Survey. This counts only families, which the government defines as households with two or more people related by birth, marriage or adoption. The graph focuses on families living in the country's 30 most populous cities.
Foot, leg, and ankle swelling. Painless swelling of the feet and ankles is a common problem, especially among older people. Abnormal buildup of fluid in the ankles, feet, and legs can cause swelling. This fluid buildup and swelling is called edema. Painless swelling may affect both legs and may include the calves or even the thighs. The effect of gravity makes the swelling most noticeable in the lower part of the body.
This pressure backs up in the heart. The higher pressure causes swelling in the legs and feet. Congestive heart failure, a condition in which the heart can no longer pump efficiently, causes fluid buildup in the lungs and other parts of the body. Swelling is often most visible in the feet and ankles. Pregnancy can cause edema in the legs as the uterus puts pressure on the vena cava. Fluid retention during pregnancy also can be caused by a more serious condition called preeclampsia. Low protein levels in the blood caused by malnutrition, kidney and liver disease can cause edema.