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Swelling of One Thigh: Causes

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Last updated March 24, 2022

Swelling of one thigh quiz

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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.

8 most common causes

Cellulitis
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Deep Vein Thrombosis
Osteogenic Sarcoma
Contact Dermatitis
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Benign bony growth (osteochondroma)
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Compartment syndrome
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Thigh bruise
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Hamstring strain

Swelling of one thigh quiz

Take a quiz to find out what's causing your swelling.

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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.

Obstructive

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

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.

Inflammatory

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

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.

Swelling of one thigh quiz

Take a quiz to find out what's causing your swelling.

Take swelling of one thigh quiz

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.

You can treat this at home with rest (exercise as tolerated), ice (10-20 minutes at a time) and elevation (put your feet up to help blood flow back to the heart using gravity).

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

Osteogenic sarcoma

Osteogenic sarcoma (osteosarcoma) is a cancer that starts in the bone, and usually affects the ends of the bone where new tissue forms at a growth plate. It is the most common cancerous bone tumor in young people, with the average age at diagnosis being 15 years. Pain in the bone is the most commonly reported symptom.

You should visit your primary care physician who will be able to coordinate your care with a cancer specialist (oncologist). This condition is treated with chemotherapy and surgery. Unfortunately, surgery may involve amputation of the entire limb.

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.

You can safely treat this condition on your own. A muscle strain can be treated with rest, ice, compression, and pain killers.

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

Deep vein thrombosis

A deep vein thrombosis (DVT) occurs when a blood clot forms in a vein deep in the body, usually in the lower leg or thigh. DVT can cause swelling, pain, and redness in the affected leg. Some of the risk factors for developing DVT include obesity, pregnancy, cancer, surgery, and previous history of blood clots.

You should consider calling your primary care or urgent care provider. Deep vein thrombosis can be evaluated with a review of your symptoms, a physical exam, and an ultrasound. A blood test may also be performed. Once diagnosed, DVT can be treated with blood-thinning medication, which is usually taken for three months.

Rarity: Uncommon

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

Urgency: Hospital emergency room

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

Cellulitis

Crohn's disease is an inflammation of the bowel. It is caused by a faulty immune system response which makes the body attack the lining of the intestines.

The disease usually appears before age thirty and can affect anyone. Those with a family history may be most susceptible. Smoking is a known risk factor.

Aggravating factors include stress, poor diet, and nonsteroidal anti-inflammatory drugs such as ibuprofen and aspirin.

Early symptoms usually develop gradually, but can appear suddenly. These include fatigue, loss of appetite, fever, mouth sores, diarrhea, abdominal pain, and blood in stool.

Untreated Crohn's disease can cause ulcers throughout the digestive tract as well as bowel obstruction, malnutrition, and deteriorating general health.

Diagnosis is made through blood test and stool sample test. Colonoscopy, CT scan, MRI, endoscopy, and/or enteroscopy may also be used.

Crohn's disease cannot be cured, but can be managed through reducing the inflammation. Antibiotics, corticosteroids, and immune system suppressors may be tried. Excellent nutrition, vitamin supplements, smoking cessation, and reduction in stress can be helpful.

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

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.

You should visit your primary care physician for X-Ray evaluation. In most cases this condition is treated by careful observation over time to make sure the tumor does not grow. Surgery is considered if the osteochondroma causes pain, puts pressure on a nearby nerve or blood vessel, or has a large cap of cartilage.

Rarity: Ultra rare

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

Urgency: Primary care doctor

Allergic contact dermatitis of the thigh

Allergic contact dermatitis means the skin has touched something that provoked an allergic reaction, causing inflammation and irritation.

"Contact" means the allergic reaction came from touching something, not from consuming something. The first exposure to the substance sensitizes the immune system, and then the second exposure actually causes the symptoms.

The most common causes of allergic contact dermatitis are:

  • Nickel, a metal often used in belt buckles, the buttons on pants, and jewelry, including piercing jewelry.
  • Poison ivy.
  • Various types of perfumes, including those founds in soaps, fabric softeners, and detergents.
  • Of course, there are many more.

Symptoms include red, itching, scaling, flaking skin that may be painful due to the irritation and inflammation.

Diagnosis is made through first avoiding contact with any suspected substance, to see if the dermatitis clears. Patch testing can be done if the results are not certain.

Treatment involves fully avoiding the allergy-provoking substance and using topical steroid cream as prescribed. Cool compresses and calamine lotion can help to ease the discomfort.

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

Swelling of one thigh quiz

Take a quiz to find out what's causing your swelling.

Take swelling of one thigh quiz

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.

Share your story
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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References

  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