Peripheral Edema: Swollen Legs and Ankles Explained

Peripheral edema most commonly affects the legs, ankles, and feet and appears as visible swelling caused by fluid collecting in the tissues. Edema occurs when small blood vessels leak fluid into surrounding connective tissue, such as skin, cartilage, or the spaces between cells.

From a first aid, CPR, and workplace safety perspective, recognizing peripheral edema is important because it can range from a temporary, harmless condition to a sign of a serious medical emergency, depending on the cause.

This article is for educational purposes only and is not a substitute for medical diagnosis or treatment.

What Is Peripheral Edema?

Peripheral edema refers specifically to swelling in areas far from the heart, most often:

Ankles
Feet
Lower legs

Gravity plays a major role, which is why swelling is more noticeable after long periods of standing, sitting, or immobility. Fluid can also accumulate in internal organs such as the lungs or heart, but that type of edema presents very differently and requires urgent medical care.

Understanding where the swelling occurs helps determine why it is happening.

Peripheral Edema Caused by Trauma or Reduced Movement

One important cause of sudden or one-sided leg swelling is deep vein thrombosis (DVT). This occurs when a blood clot forms in a deep vein—usually in the leg—and triggers inflammation and fluid buildup.

From a first aid standpoint, DVT is dangerous because:

A clot can break free
Travel through the bloodstream
Block blood vessels in the lungs (pulmonary embolism)

Peripheral edema can also occur due to:

Long airplane flights or road trips
Extended standing at work
Foot or ankle injuries
Reduced mobility after illness or injury
Excess body weight increasing pressure on veins

These situations are particularly relevant in Canadian workplaces, long-distance travel, and physically demanding occupations.

Venous Insufficiency and Chronic Swelling

Venous insufficiency occurs when the valves in the leg veins weaken or become damaged. These valves normally keep blood flowing upward toward the heart. When they fail:

Blood pools in the legs
Veins remain dilated
Fluid leaks into surrounding tissue

This leads to chronic peripheral edema, often affecting both legs and worsening by the end of the day.

Common features include:

Swelling around ankles and calves
Heaviness or aching in the legs
Visible varicose veins

This condition is common in people who stand for long hours, including many service, healthcare, and industrial workers.

Kidney and Liver Conditions

The kidneys and liver play a major role in regulating fluid balance in the body. When they are not functioning properly, fluid can accumulate in peripheral tissues.

Peripheral edema may be seen in conditions such as:

Kidney disorders that impair fluid elimination
Liver disease affecting blood protein levels
Severe systemic illnesses

In these cases, swelling is often persistent and may be accompanied by other symptoms such as fatigue, abdominal swelling, or changes in urination.

First Aid Awareness: When Edema Is a Warning Sign

Peripheral edema should not be ignored if it presents with any of the following:

One-sided leg swelling, redness, warmth, or pain
Sudden swelling after trauma
Swelling with chest pain or shortness of breath
Rapidly worsening edema
Fever or signs of infection

These situations require immediate medical assessment and are emphasized in first aid and emergency response training.

Self-Care for Mild Peripheral Edema

For mild, non-painful swelling related to gravity or activity:

Elevate legs above heart level for 30 minutes
Move regularly during long trips
Avoid prolonged standing without breaks
Wear supportive footwear
Stay hydrated and moderate salt intake

If swelling does not improve or keeps returning, medical evaluation is recommended.

Educational Disclaimer

This content is provided for general public education and first aid awareness only. It is not a medical diagnosis. Persistent, painful, or one-sided swelling should always be assessed by a healthcare professional.