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Swelling of One Thigh: Causes

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Last updated November 16, 2020

Swelling of one thigh questionnaire

Use our free symptom checker to find out what's causing your swelling.

Noticing one thigh swelling can be a cause for concern. Trauma from an injury can cause compartment syndrome which can lead to a swollen thigh above the knee. Deep vein thrombosis or a thigh bruise are also common causes of a swollen thigh.

Swelling of one thigh questionnaire

Use our free symptom checker to find out what's causing your swelling.

Swelling of one thigh symptom checker

Symptoms of swelling of one thigh

Swelling, also called edema, is the result of fluid buildup that is trapped in your body’s tissues. Most often, fluid buildup occurs when an area of the body becomes inflamed or injured. With injury or inflammation, the small blood vessels in the body begin to leak fluid and bring in white blood cells to repair the damage. As a result, more fluid follows. Depending on the cause, the swelling can be generalized and occur throughout the body, or localized and only affect a specific part of the body.

Common characteristics of swelling in one thigh

The legs are gravity-dependent — meaning gravity pulls blood down to whichever part of the body is closest to the ground — and swelling localized to one thigh is often obvious and easy to identify by the following common characteristics:

  • One thigh will appear larger than the other
  • Skin pitting: This is when the skin dimples or dents after pressing on the affected area for a few seconds.

Common accompanying symptoms

Swelling in one thigh may also be accompanied by many other associated symptoms depending on the cause:

  • Pain
  • Redness or warmth of the thigh
  • Cramping or soreness
  • Feeling of heaviness
  • Stretched or shiny skin
  • Stiffness
  • Limited range of motion

Swelling in only one thigh can be a sign of a serious underlying condition that requires prompt attention. If you notice any of these symptoms, make an appointment with your doctor as soon as possible in order to receive appropriate care.

Causes of swelling of one thigh

There are multiple causes of swelling of one thigh that range from benign to life-threatening. These causes are most easily categorized as obstructive or leakage-related. It is important to follow-up with your healthcare provider if you notice symptoms in order to get the appropriate diagnosis and care.


Fluid buildup can occur in the case of obstruction. Obstructive causes of swelling in one thigh are related to clotting of the blood that begins in the shin/lower leg. When a blood clot forms in the deep veins of the lower leg (deep vein thrombosis), it obstructs blood flow and can result in leg swelling and pain. There are different categories of how blood clots can form including:

  • Hematologic: Bleeding disorders and medical conditions such as cancer that affect the way different components of the blood function can result in blood clots.
  • Immobility: When the leg is immobile for long periods, (i.e. after surgery or traumatic injury that requires casting), the muscles do not contract normally to help blood circulate and blood clots form due to disruption of blood flow.

In the case of fluid leakage, three general mechanisms can occur that result in fluid buildup in the surrounding tissues of the thigh:

  • Excessive force or pressure inside the blood vessels
  • A force external to the blood vessel can cause fluid to be drawn out
  • Damage or destruction to the blood vessel wall leading to fluid loss


Systemic causes of fluid leakage involve conditions that affect the entire body.

  • Circulatory: Problems with the heart and its ability to pump effectively (heart failure) will cause blood to back up in the lower body. This causes excessive pressure in the blood vessels that causes damage and further leakage of fluid into the body’s tissue. Furthermore, if the veins of the circulatory system are weakened or damaged, the swelling will occur in a similar manner.
  • Lymphatic: The lymphatic system is the body’s natural way of clearing excess fluid from tissues. It is composed of multiple nodes and vessels that when damaged can cause swelling all over the body, especially the thigh and lower leg.
  • Kidney: The kidney is a potent regulator of bodily fluid because it is responsible for filtering and clearing the blood. Without the kidney, filtrate such as proteins, electrolytes, and toxins can remain in the blood and act as forces that draw fluid out. In most cases, kidney problems result in swelling of both legs and usually does not affect only one leg.

Swelling of one thigh questionnaire

Use our free symptom checker to find out what's causing your swelling.

Swelling of one thigh symptom checker


Inflammatory causes of fluid leakage cause injury to the surrounding tissues and swelling in multiple ways:

  • Arthritis: Arthritis is a general term for multiple conditions that cause painful inflammation and stiffness of the bones and joints. Arthritic processes that affect the knees and ankles can cause irritation that often leads to injury. Furthermore, arthritis in the joints of the lower extremity predisposes people to inactivity, making swelling even more likely.
  • Infection: Both superficial infections of the skin and deep tissue infections of the thigh can result in swelling. One type of deep tissue infection called necrotizing fasciitis can spread quickly and destroy tissue, resulting in a life-threatening illness that requires immediate care.


Environmental causes of swelling of one thigh may be related to lifestyle habits or certain exposures.

  • Smoking: Smoking can affect blood clotting and circulation, increasing the risk of deep vein thrombosis.
  • Medication: Swelling in one thigh can be a side effect of many medications that treat common conditions such as high blood pressure, diabetes, and menopause. However, usually, this causes swelling in both legs rather than just one.
  • Diet: Diets high in sodium can cause an overload of the body’s filtering mechanisms. The extra salt in the blood will cause fluid to be drawn out from the vessels, causing swelling. Furthermore, obesity can increase the pressure in the veins of the leg causing leakage and fluid buildup.

This list does not constitute medical advice and may not accurately represent what you have.

Compartment syndrome

Acute compartment syndrome describes the damage done to certain muscle groups of the arms or legs after a traumatic injury.

All of the long muscles are bundled into sections – "compartments" – by the white sheets of strong, tough connective tissue called fascia. If something interferes with circulation so that blood flow is trapped within the compartment, pressure rises because the fascia cannot stretch. This causes serious damage to the muscles and other tissues within the compartment.

Acute compartment syndrome is caused by a broken bone; a crush injury; burns, due to scarred and tightened skin; and bandages or casts applied before an injury has stopped swelling.

Symptoms can rapidly intensify. They include severe pain and tightness in the muscle; tingling or burning sensation; and sometimes numbness and weakness.

Acute compartment syndrome is a medical emergency which can result in loss of the limb. Take the patient to the emergency room or call 9-1-1.

Diagnosis is made through patient history and physical examination.

Treatment involves hospitalization for emergency surgery and, in some cases, skin graft.

Rarity: Rare

Top Symptoms: arm numbness, hand numbness, foot numbness, pain in one leg, thigh numbness

Urgency: Hospital emergency room

Deep vein thrombosis

Deep vein thrombosis (DVT) is a blood clot that forms in a vein deep in the body. Most deep vein clots occur in the lower leg or thigh.

Rarity: Uncommon

Top Symptoms: fever, thigh pain, upper leg swelling, calf pain, butt pain

Urgency: Hospital emergency room

Hamstring strain

A strain, commonly called a "pulled muscle," is when a muscle becomes overstretched and tears. A hamstring strain happens when one of the muscles on the back of the upper leg (thigh) is pulled.

Rarity: Uncommon

Top Symptoms: spontaneous back pain, pain in the back of the knee, hamstring tightness, sports injury, hamstring pain

Symptoms that always occur with hamstring strain: hamstring pain

Symptoms that never occur with hamstring strain: groin pain, hip pain, pain in the outside of the hip, difficulty moving the hip

Urgency: Self-treatment

Thigh bruise

A bruise is the damage of the blood vessels that return blood to the heart (the capillaries and veins), which causes pooling of the blood. This explains the blue/purple color of most bruises.

Rarity: Rare

Top Symptoms: pain in one thigh, thigh pain from an injury, upper leg injury, thigh bruise, swelling of one thigh

Symptoms that always occur with thigh bruise: upper leg injury, thigh pain from an injury

Urgency: Self-treatment


Cellulitis is a bacterial infection of the deep layers of the skin. It can appear anywhere on the body but is most common on the feet, lower legs, and face.

The condition can develop if Staphylococcus bacteria enter broken skin through a cut, scrape, or existing skin infection such as impetigo or eczema.

Most susceptible are those with a weakened immune system, as from corticosteroids or chemotherapy, or with impaired circulation from diabetes or any vascular disease.

Symptoms arise somewhat gradually and include sore, reddened skin.

If not treated, the infection can become severe, form pus, and destroy the tissue around it. In rare cases, the infection can cause blood poisoning or meningitis.

Symptom of severe pain, fever, cold sweats, and fast heartbeat should be seen immediately by a medical provider.

Diagnosis is made through physical examination.

Treatment consists of antibiotics, keeping the wound clean, and sometimes surgery to remove any dead tissue. Cellulitis often recurs, so it is important to treat any underlying conditions and improve the immune system with rest and good nutrition.

Rarity: Uncommon

Top Symptoms: fever, chills, facial redness, swollen face, face pain

Symptoms that always occur with cellulitis: facial redness, area of skin redness

Urgency: Primary care doctor

Osteogenic sarcoma

Osteogenic sarcoma is a cancer of the bone that usually develops when bones are rapidly growing during adolescence. It is the most common primary tumor of the bone. Although any bone in the body can be affected, the thigh (femur), upper arm (humerus), shin (tibia), and pelvis are mo..

Allergic contact dermatitis of the thigh

Allergic contact dermatitis is a condition in which the skin becomes irritated and inflamed following physical contact with an allergen. Common products known to cause allergic dermatitis include plants, metals, soap, fragrance, and cosmetics.

Rarity: Common

Top Symptoms: upper leg itch, upper leg redness, scabbed area of the upper leg

Symptoms that always occur with allergic contact dermatitis of the thigh: upper leg redness

Urgency: Self-treatment

Benign bony growth (osteochondroma)

An osteochondroma is a non-cancerous growth that usually develops during childhood or adolescence. It is a benign tumor that forms on the surface of a bone near the growth plate.

Rarity: Ultra rare

Top Symptoms: lower leg bump, upper leg bump, numbness in one thigh, painful thigh lump, hip bump

Urgency: Primary care doctor

Swelling of one thigh questionnaire

Use our free symptom checker to find out what's causing your swelling.

Swelling of one thigh symptom checker

Swelling of one thigh treatments and relief

At-home treatments

Fortunately, many strategies and remedies you can perform at home can mitigate swelling in the calves, legs, and thigh:

  • Activity: Moving your legs and staying active can help pump any excess fluid pooling in the legs back toward your heart. Talk to your doctor about exercises you can do at home in order to keep moving.
  • Elevate: Place your legs above the level of your heart as much as possible. Elevating the legs during sleep can help significantly with thigh swelling. Compress: Your doctor may prescribe compression stockings for your legs. These garments keep the pressure on your limbs to prevent fluid from collecting in the tissue.
  • Protect: Keep your swollen thigh clean and free from injury. Dry, cracked skin is more prone to scrapes, cuts, and infection.
  • Dietary changes: Reducing salt intake, losing weight and quitting smoking can be an important step in reducing your swelling.

When to see a doctor

Treatment for obstructive causes of swelling in one thigh involves prevention of the formation of blood clots. Several medications work to thin the blood, break up clots and filter clots that break off and travel through the circulation away from the lungs.

Systemic causes of thigh swelling are often treated with medication. Your doctor may suggest:

  • Diuretics: These are medications, also known as “water pills,” that increase the water and salt your body excretes in the urine. This strategy helps reduce the fluid trapped in the body and your legs.
  • Non-inflammatory medications: Your doctor may prescribe this type of medication to combat arthritic processes that are causing swelling.

When it is an emergency

Seek medical attention immediately if you experience:

  • Sudden-onset of swelling in one leg associated with pain
  • Shortness of breath
  • Chest pain

This can signify that a clot causing a deep vein thrombosis (DVT) that has traveled to the lungs in a condition called pulmonary embolism (PE). A pulmonary embolism is a life-threatening emergency that requires immediate attention.

FAQs about swelling of one thigh

Why is the swelling in only one thigh?

The swelling is localized to one leg due to obstruction of a deep vein in the leg or because of an infection or other inflammatory condition specifically affecting that extremity.

What tests are usually performed for swelling in one thigh?

One test your physician may perform is an ultrasound of the affected thigh. An ultrasound is a device that sends sound waves through the tissues of the leg and uses a computer to convert the sound waves into an image on a screen. Your doctor will be able to visualize a blood clot if it is present.

Can a clotting disorder be inherited?

Yes, clotting disorders can be inherited. Be suspicious of an inherited clotting disorder if you and other members of your immediate family have experienced blood clots or complications of blood clots such as pulmonary embolism or multiple miscarriages.

Can I travel with swelling in one thigh?

It is not advisable to travel with swelling in one thigh. Traveling, especially for a long flight or drive, can cause increased disruption of blood flow in the thigh. The muscles contract less and can further exacerbate a possible clot in the leg that is causing the swelling.

What can I do to prevent immobility in my thigh/lower leg on long flights or drives?

Moving as much as possible during a flight can help reduce periods of prolonged immobility. For example, getting up to go to the bathroom or to walk up and down the aisle every two hours can go a long way in keeping the body active [5]. If you cannot get up, perform seated exercises such as ankle circles, leg raises or foot/calf pumps in order to prevent immobility. Avoid placing hand luggage in places that restrict movement of the legs and wear loose, comfortable clothing.

Questions your doctor may ask about swelling of one thigh

  • Do you have a rash?
  • Any fever today or during the last week?
  • Have you ever been diagnosed with diabetes?
  • Have you been feeling more tired than usual, lethargic or fatigued despite sleeping a normal amount?

Self-diagnose with our free Buoy Assistant if you answer yes on any of these questions.

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Dr. Rothschild has been a faculty member at Brigham and Women’s Hospital where he is an Associate Professor of Medicine at Harvard Medical School. He currently practices as a hospitalist at Newton Wellesley Hospital. In 1978, Dr. Rothschild received his MD at the Medical College of Wisconsin and trained in internal medicine followed by a fellowship in critical care medicine. He also received an MP...
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  1. Foot, leg, and ankle swelling. U.S. National Library of Medicine: MedlinePlus. Reviewed May 21, 2017. MedlinePlus Link
  2. Gorman WP, Davis KR, Donnelly R. Swollen lower limb: general assessment and deep vein thrombosis. West J Med. 2001;174(2):132–136. NCBI Link
  3. Lymphedema (PDQ)–Patient Version. National Cancer Institute. Updated May 29, 2015. National Cancer Institute
  4. Necrotizing Fasciitis: All You Need to Know. Centers for Disease Control and Prevention. Updated Oct. 18, 2018. CDC Link
  5. Immobility, circulatory problems and deep vein thrombosis (DVT). World Health Organization. WHO Link