Noticing swelling in one foot only can be unsettling, especially when the other foot looks normal. This uneven swelling can happen for several reasons, including deep vein thrombosis, chronic venous insufficiency, peripheral arterial disease, lymphedema, infection, or something as simple as an injury.

Some causes are minor and temporary, but others need medical attention right away. If your foot swelling won’t go away, causes discomfort, or worries you, it’s always smart to talk with a healthcare provider for proper evaluation and diagnosis.

What Causes Swelling in One Foot Only?

Chronic Venous Insufficiency (CVI)

Chronic venous insufficiency occurs when the valves in your leg veins become damaged or weakened. When this happens, it becomes difficult for your blood to flow back to your heart, and it begins to pool in the lower portions of your leg and foot.

This condition typically develops gradually and often affects people who spend long periods standing or sitting. You might notice that the swelling is worse at the end of the day and improves somewhat after you’ve been lying down with your feet elevated.

In my practice, I see patients with CVI who often describe these common symptoms:

• Swelling that starts in the ankle and foot area
• Aching or cramping in the affected leg
• Skin that feels tight or looks shiny
• Visible varicose or spider veins
• Discolored skin, particularly around the ankle
• A heavy or tired feeling in the leg

You might also experience leg swelling in only one leg.

Lymphedema

Lymphedema is a chronic condition where your lymphatic system can’t properly drain lymph fluid from your tissues. 

This system normally acts like your body’s drainage network, collecting excess fluid, proteins, and waste products from your tissues and returning them to your bloodstream. When this system becomes impaired, fluid accumulates in the affected area, causing swelling.

The fluid buildup usually happens because of secondary lymphedema, which is the most common type of the condition. It develops after something damages or blocks your lymphatic vessels. This damage can come from cancer treatments (especially lymph node removal or radiation), surgeries, infections, injuries, or certain medical conditions.

Lymphedema often affects just one limb, which explains why you might have swelling in only one foot.

After treating hundreds of patients with lymphedema, I can tell you that key signs include:

• Swelling that may start in your toes and gradually move up your foot and leg
• A feeling of heaviness, fullness, or tightness in the affected area
• Trouble fitting into shoes that previously fit well
• Less flexibility in your ankle or toes
• Skin that appears stretched or feels firm to the touch
• In later stages, the skin may become thicker and develop a bumpy texture

Lymphedema tends to be progressive, which means that it’ll gradually get worse if left untreated.

The good news is that treatment for lymphedema typically involves a comprehensive approach called Complete Decongestive Therapy (CDT). This includes:

• Manual lymphatic drainage, a specialized massage technique that helps redirect lymph fluid to working lymph nodes
• Gentle physical exercise to activate your muscle pump and improve lymph flow
• Compression therapy using bandages or specially fitted garments to manage the swelling
• Skin care because keeping your skin clean, moisturized, and protected from cuts or scratches helps prevent complications

Here’s what’s encouraging, especially in its early stages, lymphedema can respond very well to treatment. Sometimes, it’s even possible to naturally reverse the swelling.

Deep Vein Thrombosis (DVT) 

Deep vein thrombosis is a serious condition where a blood clot forms in one of the deep veins in your body, often in your leg or foot. This clot blocks normal blood flow, causing fluid to back up and create swelling in the affected area.

DVT requires immediate medical attention because the blood clot can potentially break loose and travel to your lungs, creating a life-threatening situation called a pulmonary embolism.

If you think you might have DVT, don’t wait and seek emergency medical care right away.

DVT symptoms often show up suddenly and may include:

• Sudden swelling in one foot or leg
• Pain or tenderness that may worsen when you walk or stand
• Warmth in the affected area
• Red or discolored skin
• Visible enlarged veins
• A cramping sensation that doesn’t improve with rest

Some things increase your risk of developing DVT, including prolonged periods of not moving or inactivity (like long flights or bed rest after surgery), recent surgery, pregnancy, hormone therapy, obesity, smoking, and certain medical conditions that affect blood clotting.

Injury

Sometimes the simplest explanation is the right one.

An injury to your foot, such as a sprain, strain, fracture, or even a bad bruise, can cause swelling that affects only that foot. Your body’s natural response to injury is inflammation, which brings extra blood flow and fluid to the damaged area to help with healing.

Injury-related swelling usually comes with other clear signs like pain at the injury site, bruising, trouble walking or putting weight on the foot, and tenderness when you touch the area.

This type of swelling typically improves as your injury heals, often within a few days to weeks, depending on how severe the damage was.

Peripheral Artery Disease (PAD)

Peripheral arterial disease happens when the arteries that carry blood to your legs and feet become narrowed or blocked, usually due to a buildup of fatty deposits. This reduces blood flow to your lower extremities and can cause swelling, though it’s less common than with vein problems.

PAD symptoms include:

• Swelling in one or both feet
• Cramping or pain in your legs when walking that goes away when you rest
• Coldness in your foot or leg
• Weak pulse in your feet
• Slow-healing wounds or sores on your feet or legs

Your swollen foot might also appear pale or bluish in color.

Infection

Infections in your foot can cause localized swelling as your immune system fights off bacteria or other harmful organisms. Cellulitis is one of the most common types of skin infections that can affect your foot and lower leg.

With cellulitis, bacteria enter your skin through a cut, scrape, or crack and spread into the deeper layers of tissue. The infected area becomes swollen, red, warm to the touch, and painful. You might also notice red streaks coming from the swollen area, and some people develop a fever.

Cellulitis isn’t contagious because it’s a bacterial infection, but it needs prompt antibiotic treatment to prevent it from spreading to other parts of your body. If you think you might have cellulitis, get medical care immediately.

Liver Disease

When your liver isn’t working properly, it can’t make enough of a protein called albumin, which helps keep fluid in your blood vessels. Without enough albumin, fluid leaks out into your tissues, causing swelling that often starts in your feet and ankles.

Liver-related swelling usually affects both feet, but sometimes one foot swells more than the other. Other signs of liver problems include yellowing of your skin or eyes, fatigue, nausea, abdominal swelling, and dark-colored urine.

Kidney Disease

Your kidneys filter waste and extra fluid from your blood. When they’re not working well, excess fluid and salt can build up in your body, leading to swelling. Like liver disease, kidney problems typically cause swelling in both feet, but one side can be more affected.

Swelling in One Foot Only, No Pain

When your foot is swollen but doesn’t hurt, it’s often because of fluid retention or circulation issues, not an injury or infection. One of the most common causes is lymphedema, which develops gradually and creates a feeling of heaviness rather than sharp pain. Chronic venous insufficiency can also cause painless swelling, especially at the end of the day.

Swelling in One Foot Only with Pain

Painful swelling in one foot often signals a more urgent problem that needs quick attention. Deep vein thrombosis is one of the most serious causes, typically causing sudden swelling along with warmth, redness, and significant pain or tenderness. Infections like cellulitis also create painful, warm, and red swelling. If the swelling is painful, seek immediate medical care.

When to See a Doctor for Foot and Ankle Swelling

Seek immediate medical care if you experience sudden, severe swelling in one foot, especially with pain, warmth, or redness. Also, get emergency help if you have swelling along with chest pain, difficulty breathing, or dizziness, as these might mean a serious heart or lung problem.

Even painless swelling deserves medical attention if it persists for more than a week and affects your daily activities. Here’s the thing: with a condition like lymphedema, early diagnosis and treatment can minimize or even naturally reverse the chronic swelling.

When working with my patients, I often coordinate care with vascular specialists for circulation issues, or a physiatrist for lymphedema. The key is getting the right specialist involved at the right time.

Living with Leg Lymphedema or Chronic Foot Swelling

If lymphedema is causing your foot swelling, it’s important to understand that it’s a chronic condition you’ll need to manage long-term. Without proper management, the swelling will persist and get worse. But with proper treatment and self-care, you can reduce symptoms and live a full, active life.

If you’re dealing with lymphedema or chronic foot swelling, I’ve created comprehensive resources in my program, Lower Body Lymphedema Rehab!