Popliteal Vein Thrombosis or Baker’s Cyst?

Medically Reviewed by James Beckerman, MD, FACC on June 03, 2022

Popliteal vein thrombosis happens when a blood clot blocks one of the blood vessels behind your knees. It’s a serious condition, but it can sometimes be mistaken for a less-dangerous condition called a Baker’s cyst.

What Is Popliteal Vein Thrombosis?

Your popliteal vein is one of the blood vessels that carries blood from your legs back to your heart. It runs behind your knee and up the back of your thigh. It’s one of the vessels doctors call a “deep vein” because it’s far underneath your skin.

Sometimes the blood flowing through those veins can form a clot -- a thick clump that can keep blood from getting through smoothly. The medical term for a blood clot is “thrombosis,” and it can be dangerous if it happens in a blood vessel like the popliteal vein.

That’s because blood clots in deep veins can travel to your lungs and block a blood vessel there. That's called a pulmonary embolism, and it can be deadly.

What Is a Baker’s Cyst?

This forms when your body makes too much of the fluid that keeps your knee joint moving smoothly. It can happen if you hurt your knee or have a condition that affects your joints, like arthritis. It’s also called a popliteal cyst because it forms at the back of your knee.

A Baker’s cyst can make your knee feel swollen, stiff, or uncomfortable. In rare cases, it can break open and cause fluid to leak down into your lower leg. That can hurt and lead to more swelling.

Similar Symptoms

A blood clot in the popliteal vein and a Baker’s cyst have many common symptoms. That can make it hard for your doctor to know which one you have, especially if the cyst has broken open.

Signs of both conditions include:

  • Swelling in your leg
  • Pain when you stand or walk
  • Redness or warmth in the swollen area

Which Is Which?

Your doctor’s first step will be to look for signs of swelling then feel the area around the back of your knee as you flex it.

If that doesn’t give them enough information, they’ll probably recommend an imaging test to get a better picture of what’s going on. These might include:

  • Ultrasound, which uses high-frequency sound waves to make a live picture of the inside of your leg on a monitor. The kind of ultrasound used to look for signs of deep vein blood clots is called venous duplex scanning.
  • MRI, which uses powerful magnets and radio waves to make a detailed picture of the inside of your legs.
  • Venography, which uses a dye to help show problems inside your blood vessels. The dye gives your doctor an idea of how blood is flowing inside your veins.
  • A blood test known as the D-dimer test, which measures a protein that’s linked to clots.

For a Baker’s cyst, most of your symptoms can be treated with ice and over-the-counter painkillers. If you have popliteal vein thrombosis, you may need medicine to treat the clot before it can cause bigger problems.

Show Sources


National Heart, Lung, and Blood Institute: “Deep Vein Thrombosis.”
The Mayo Clinic: “Baker’s cyst.”

National Health Service (UK): “Baker’s cyst.”

Journal of Vascular Surgery: “Baker's cysts mimicking the symptoms of deep vein thrombosis.”

Sports Medicine: “Baker’s Cyst - Diagnostic and Surgical Considerations.”

Emergency Medicine: “Baker's cyst rupture may mimic deep vein thrombosis.”

Revista Brasileira de Ortopedia: “Baker’s Cyst.”

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