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Leg swelling, also known as edema, can be a cause for concern, especially when it occurs in only one leg. While a swollen ankle after a long day or puffiness after a plane ride might seem normal, only your left leg swelling can signal an underlying medical condition.

This blog explores the potential causes of swelling in only the left leg and highlights why it is important to get a proper medical evaluation for timely diagnosis and treatment.

What is Your Swollen Leg Telling You?

Edema occurs when extra fluid accumulates in the body’s tissues, causing them to swell. This fluid buildup can happen for various reasons, like inflammation, poor lymphatic drainage, or problems with circulation.

Usually, both legs swell equally. However, in some cases, specific factors can lead to swelling in just one leg.

The Importance of Our Fluid Balance Systems

Our bodies maintain a delicate balance of fluids through two crucial systems: the lymphatic and circulatory systems.

  • The lymphatic system acts like a drainage network of thin vessels that transports excess fluid and waste products away from tissues. This fluid then travels to lymph nodes, where it gets filtered before returning to the bloodstream.
  • The circulatory system, consisting of arteries and veins, is responsible for blood flow. Blood vessels in the legs help return blood from your lower extremities to the heart.

Disruptions in either of these systems can lead to fluid accumulation. This buildup manifests as swelling in just one leg, medically known as unilateral leg swelling. (In your case, it’s affecting your left leg.)

Common Causes of Unilateral Leg Swelling

Here are some more common causes of swelling in just one leg:

1. Deep Vein Thrombosis (DVT)

DVT is a blood clot that forms in a deep vein, usually in the leg. While DVT can occur in both legs, it often affects only one. Symptoms of DVT can include:

  • Swelling in one leg, often accompanied by pain or tenderness.
  • Redness or warmth in the affected area.
  • Increased leg size.

DVT is a serious condition that requires immediate medical attention. If left untreated, a blood clot can break loose and travel to the lungs, potentially causing a life-threatening pulmonary embolism.

2. Lymphedema

Lymphedema is a condition characterized by chronic swelling caused by a blockage or damage to the lymphatic system. Fluid buildup in one leg or arm can cause significant swelling and discomfort.

Several factors can contribute to lymphedema, including:

  • Lymph node removal or damage during surgery, often related to cancer treatment.
  • Infection or inflammation in the lymph nodes.
  • Parasitic infections (rare in developed countries).
  • Certain genetic conditions.

3. Injury or Trauma

An injury to the leg, such as a sprain, fracture, or muscle strain, can cause inflammation and swelling in the affected area. This reaction is the body’s attempt to heal itself.

However, if the swelling persists or worsens, you must seek medical evaluation to rule out more serious underlying conditions.

4. Venous Insufficiency

Venous insufficiency occurs when the veins in the legs struggle to return blood effectively to the heart. This can lead to fluid buildup and swelling, particularly in the lower legs.

Risk factors for venous insufficiency include obesity, pregnancy, a history of blood clots, and varicose veins. Symptoms can include leg swelling that worsens throughout the day, heaviness or achiness in the legs, and changes in skin texture.

5. Infection

An infection like cellulitis, a bacterial skin infection often occurring on the lower legs, can cause localized swelling, redness, and pain in one leg. Prompt antibiotic treatment is essential to prevent the infection from spreading and causing further complications.

When to Seek Medical Attention?

If you experience persistent swelling in only your left leg, worsening, or other concerning symptoms such as pain, redness, or fever, it’s important to seek medical attention promptly.

Early diagnosis and treatment of the underlying cause can prevent complications and promote a full recovery.


Swelling in only your left leg can result from various medical conditions, some requiring prompt attention. If you experience this, consult Memorial Cardiology Associates for a diagnosis and treatment. Contact us today at (713) 464-6006.

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