What Are the Causes of Leg Swelling Below the Knee?

Leg swelling can be a seriously debilitating condition that hinders you from performing basic tasks of the day. The condition can worsen with time if left untreated. Several diseases have a direct link with swelling in the legs below knee level. Some of these underlying maladies are mild, while some are life-threatening. 

So, if you notice extra pressure, swelling, or heaviness in your lower legs, this article is for you. Read on to learn about the potential causes of leg swelling below the knee.

Common Causes of Leg Swelling

Leg swelling typically occurs due to two primary reasons: fluid retention and inflammation. In the vast majority of cases, swelling results from fluid accumulation in the legs, clinically known as peripheral edema. 

Peripheral Edema

The term peripheral edema is used to describe the excessive fluid build-up in the legs and is common in individuals above 50 years of age. Peripheral edema, or fluid retention, is not a disorder but a presentation of different underlying serious conditions. These may include:

Deep Venous Thrombosis (DVT)

DVT, or deep venous thrombosis, is a condition that arises due to the formation of blood clots in the legs (most commonly in the deep calf vein). Patients suffering from the condition often notice swelling in the legs accompanied by pain.

Research shows that pain, redness, and swelling of the affected leg are common presenting features of DVT. Obesity and living a sedentary life can contribute to the development of clots in the lower legs. Anticoagulant therapy is used to treat the disease.

May-Thurner Syndrome

A somewhat neglected cause of swelling in the leg below knee level is May-Thurner syndrome (MTS). This disease affects the blood flow from the legs and pelvis to the heart. The underlying cause of this syndrome is compression of the iliac vein. Thus, it is also known as iliac vein compression syndrome.

Patients may notice significant tenderness and leg swelling. Symptoms usually come and go depending upon your activity. As per a case study, a 30-year-old female presented with left leg swelling that persisted for four weeks. Swelling increases with activity. Investigations revealed that the edema was due to May-Thurner syndrome.

Heart Failure

A serious cause of peripheral edema and leg swelling is congestive heart failure. Patients with progressed state of heart failure develop pulmonary congestion and peripheral edema. The inability of the heart to properly pump blood to the body leads to the backing up of blood in the extremities.

A study revealed that 78% of heart failure patients presented with lower extremity edema. In 40% of the patients, lower leg edema was present, while 22% had swelling in the ankle region.

Three different types of edema are found in association with heart failure, i.e., pitting edema (in feet and legs), peripheral edema, and pulmonary edema (in the lower leg).

Pulmonary Hypertension

High blood pressure affecting the arteries of the lungs is termed pulmonary hypertension. Bilateral leg edema was found in several patients with pulmonary hypertension. Swelling below the knees is more common in obese patients. Edema and swelling are most prominent in the ankle region.

Researchers have found a link between pulmonary hypertension and heart failure. If both conditions coexist, edema is more pronounced.

Kidney Disease

Maladies of the kidney can also lead to fluid accumulation in the legs. When kidneys fail to remove sodium and water from the body, the accumulation can lead to peripheral edema. Critically ill patients have a high risk of developing acute kidney injury and peripheral edema.

Lymphedema

Like tissue fluid, lymph (protein-rich fluid in the lymphatic channels) can cause tissue swelling by leaking into the arms and legs. Lymphatic system abnormalities, cancer, and their treatment can trigger lymphedema. Research shows that leg swelling due to lymphedema worsens on standing.

Varicose Veins and Venous Insufficiency

Your lower legs might get physically swollen due to swelling of the leg veins. The varicose vein is a condition in which superficial skin veins become twisted and inflamed. This also pushes the fluid into the surrounding tissues. Individuals involved in jobs that require standing for long periods (such as nurses) are more prone to acquiring the condition.

Chronic venous insufficiency (CVI) is a prevalent venous infirmity of the legs. Lower extremity edema is a common feature of CVI. Pooling of blood in the legs occurs because leg veins cannot return the blood to the heart.

Pregnancy

Expecting mothers might also notice changes in the thickness of the lower extremities. As per a study, 50% of pregnant ladies experience swelling in the region below the knee (leg, ankle, and foot). That can be accompanied by leg and hip pain. Doctors suggest exercises to reduce pregnancy-related edema and swelling.

Inflammatory Conditions

Patients suffering from inflammatory conditions may also encounter leg swelling below the knee.

Injury or Trauma 

Blunt injury or leg trauma can lead to muscle strains. Injury and consequent inflammation of the legs lead to swelling. Calf strains may also present in the form of leg swelling.

Bee Sting

Getting stung by a bee can also cause localized swelling in the leg. Your leg can become swollen in response to it.

Infection

Cellulitis is a condition of bacterial skin infection that manifests in swelling, redness, and pain. Lower leg swelling can be a characteristic of cellulitis and lymphedema.

Arthritis

Osteoarthritis of the knee can cause leg swelling around the knee region. Arthritis in the ankle is also linked to swelling in the feet and legs.

Prevention and Home Care 

The following are some effective self-care tips that can help reduce leg swelling in your legs: 

• Massage the affected area with slight pressure to push away and remove the excess fluid 
• Rest a cold press for 20 minutes several times a day a the site of the swelling
• Wear compression stockings to apply consistent pressure on the affected area and prevent fluid build-up in the tissue
• Keep the affected leg in an elevated position as it can help move the excess fluid to the heart
• Take over-the-counter (OTC) anti-inflammatory medicines

When Is Leg Swelling a Serious Condition?

You must immediately visit a healthcare provider or doctor if experiencing any of these symptoms: 

• Difficulty breathing or shortness of breath
• Chest congestion or pain
• A fever higher than 100℉
• Feeling dizzy or weak

Mild swelling in the lower legs is generally not a major cause of concern and resolves in a few days. However, if the swelling persists for several days, it is essential to seek medical care. The doctor might perform imaging tests like an X-ray or ultrasound to diagnose the root cause of leg swelling below the knee and suggest the appropriate treatment.

Schedule a consultation to find out if the Center for Vascular Medicine can help with your condition.