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.