Ankles swell when fluid is retained for any reason, a condition also called peripheral edema. Ankle swelling can also occur as a result of injury or trauma to the extremity. It is normally painless, unless the ankle is injured, but the swollen area may feel tight and puffy. Ankle swelling without an obvious cause should be medically evaluated.
Pregnancy
Ankle swelling commonly occurs in pregnancy because the fluid volume in the body increases during pregnancy. Fluid return from the lower extremities is impeded by pressure on the veins that return blood to the heart from the enlarged uterus. Ankle swelling in pregnancy can indicate more severe problems such as preeclampsia, a complication related to increased blood pressure, fluid retention and sudden weight gain, obstetrician Roger Harms, M.D. reports on the MayoClinic.com website. Development of a blood clot in the lower leg can also cause ankle swelling, which may be painful.
Lymphedema
Lymphedema results when lymph fluid can't properly drain from the lymphatic system. Lymphedema most often occurs after injury to the lymph vessels, which can occur during surgery or after lymph node removal for cancer. The decreased number of lymph vessels to process the fluid leads to swelling. Lymphedema can also occur as a congenital disease which may not manifest itself until later in life, the Merck Manuals Online Medical Library explains. People with congenital disease have fewer lymph vessels than normal, which results in a backup and pooling of fluid in the lower extremities. Early in congenital lymphedema, swelling disappears with elevation and rest but later in the disease, the swelling worsens and is always present.
Heart Failure
Congestive heart failure occurs from a number of heart conditions. When the heart can't pump effectively due to injury or congenital abnormality, fluid backs up in the heart and eventually into the lower extremities. High blood pressure, coronary artery disease, valve disease, infection of the heart muscle and scar tissue from previous heart attack can all cause congestive heart failure that leads to ankle swelling, the American Heart Association explains.
Injury
Ankle sprains are common injuries to the ligaments that attach ligaments to bones. If ligaments are stretched too far, they can tear, causing pain and swelling. A severe sprain can cause injury to the soft tissues in the ankle as well, resulting in severe swelling that may require casting. A completely torn ligament may require surgical repair, the American Academy of Orthopedic Surgeons states. Broken bones in the feet or lower leg or muscle tears, called strains, can also cause injury-related ankle swelling.
