If your legs feel unusually full, tight, or pressurized—especially after standing or sitting for long periods—you might assume it’s just fatigue from a busy day. While occasional heaviness in the legs is common, persistent pressure or fullness can sometimes point to an underlying circulation issue.
One lesser-known cause of these symptoms is May-Thurner syndrome, a vascular condition that affects blood flow in the pelvis and legs. Although many people have never heard of it, May-Thurner syndrome can contribute to leg pressure, swelling, and other symptoms related to poor circulation.
Understanding how this condition affects blood flow can help explain why your legs may feel uncomfortable by the end of the day.
How Blood Normally Circulates From the Legs
Your circulatory system relies on veins to carry blood from the legs back to the heart. Because this blood must travel upward against gravity, veins use a combination of one-way valves and muscle movement to keep blood flowing in the right direction.
When you walk or move your calf muscles, those muscles help push blood upward through the veins. This system allows circulation to work efficiently even when you spend time standing or sitting.
However, when something interferes with blood flow in the large veins of the pelvis, pressure can build in the veins of the legs. This can lead to symptoms such as fullness, heaviness, or swelling.
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What Is May-Thurner Syndrome?
May-Thurner syndrome occurs when the right iliac artery compresses the left iliac vein deep within the pelvis. This compression can partially restrict blood flow from the left leg back toward the heart.
Over time, this pressure may slow circulation and cause blood to pool in the veins of the leg. As a result, people with May-Thurner syndrome may develop symptoms that worsen throughout the day.
The condition most commonly affects the left leg, although symptoms may sometimes be felt in both legs.
Why May-Thurner Syndrome Can Cause Leg Pressure
When a vein becomes compressed, blood flow may become restricted. This restriction can increase pressure inside the veins of the leg, which may lead to the sensation that the leg feels tight, full, or swollen.
Because blood has more difficulty traveling upward toward the heart, the pressure in the veins can gradually build throughout the day. This is why symptoms often feel worse in the evening and improve after resting or elevating the legs.
Many people describe the sensation as their leg feeling heavy, tight, or almost pressurized.
Symptoms of May-Thurner Syndrome
The symptoms of May-Thurner syndrome can vary from person to person. Some people may have mild symptoms, while others may experience more noticeable circulation problems.
Common symptoms associated with May-Thurner syndrome include:
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A feeling of fullness or pressure in the leg
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Leg heaviness or fatigue, especially later in the day
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Swelling in the lower leg or ankle
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Visible varicose veins
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Aching or discomfort after standing for long periods
Because the condition typically affects the left iliac vein, symptoms are often more noticeable in the left leg.
How May-Thurner Syndrome Is Diagnosed
Diagnosing May-Thurner syndrome usually begins with a circulation evaluation by a vascular or vein specialist. Doctors often start with a duplex ultrasound to assess blood flow in the veins of the legs.
However, because May-Thurner syndrome occurs deep within the pelvis, additional imaging may sometimes be needed to confirm the diagnosis. This may include advanced imaging tests that allow doctors to see whether the iliac vein is being compressed.
These tests help specialists determine whether vein compression is contributing to a patient’s symptoms.
Treatment Options for May-Thurner Syndrome
Treatment for May-Thurner syndrome focuses on restoring healthy blood flow through the affected vein. In many cases, minimally invasive procedures can help relieve the compression and improve circulation.
Depending on the severity of the condition, treatment options may include:
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Procedures that open the compressed vein to improve blood flow
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Placement of a stent to keep the vein open
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Additional vein treatments if varicose veins or venous reflux are also present
These procedures are typically performed in specialized vascular centers and often allow patients to return to normal activities relatively quickly.
When to See a Vein Specialist
Occasional leg fatigue or heaviness can happen to anyone after a long day. However, persistent symptoms—especially if they affect one leg more than the other—may indicate an underlying circulation issue such as May-Thurner syndrome.
A vein specialist can evaluate your symptoms, examine your circulation, and determine whether further testing is needed.
If your legs frequently feel full, tight, or pressurized by the end of the day, scheduling a consultation can help identify the cause and determine whether treatment may improve your comfort and circulation.
