Ultrasound Guided Baker’s Cyst Aspiration

Aspirating a Baker’s cyst can be a fast, low risk, bedside procedure that we perform in the office. We use ultrasound guidance to locate and evaluate the baker’s cyst. After prepping the area and using local anesthetic, a small needle is used to enter the cyst and we can watch as the fluid is aspirated. We can consider putting steroid or PRP into the joint space to help decrease the inflammation that caused the joint fluid to accumulate.

Learn more about Baker’s cysts

What is a Baker’s cyst?

A Baker’s cyst is a fluid-filled swelling that can develop behind the knee. It is named after a doctor called Dr. William Baker first described this condition in 1877. It is also sometimes called a popliteal cyst, as the medical term for the area behind the knee is the popliteal fossa. They can be small and asymptomatic or be as large as a couple centimeters. The pain caused by these cysts is usually secondary to the effects of pressure on the surrounding muscle and tissues.

What causes a Baker’s cyst?

Baker’s cysts are most commonly secondary to an underlying knee problem, such as osteoarthritis or rheumatoid arthritis. The knee joint space is surrounded by something called a joint capsule. The function of the capsule is to keep the outside muscle, blood, and tissues outside of the knee joint and the synovial fluid inside this contained area.

The joint capsule is a thick structure that surrounds your whole knee and gives it some support. It is lined by a special membrane called the synovium. The synovium produces a fluid called synovial fluid. This fluid acts as a lubricant within your knee joint and helps to cushion it during movement.

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When you have arthritis or inflammation within the knee, synovial (joint space) fluid is formed and collects within this closed space. If enough fluid accumulates, it pushes this in all directions, and can be appreciated in the front, on the sides of the knee caps. If enough accumulates, it can also push backwards, as there is more space behind the knee than in front, and form a cyst. This is known as a secondary Baker’s cyst.

There is another type of Baker’s cyst that presents in children and is much less common. This is known as a primary Baker’s cyst.

Does a Baker’s cyst cause any symptoms?

In general, the larger the Baker’s cyst, the more likely it is to produce symptoms. You may be able to see or feel the swelling behind your knee. Sometimes you may also notice that the knee joint itself is swollen. Some people feel an ache around the knee area. It may be difficult to bend your knee if you have a large Baker’s cyst and the area behind your knee may feel tight, especially when you are standing up.

Are there any complications that can develop?

The most common complication of a Baker’s cyst is for it to rupture (split open). If this happens, the fluid from inside the cyst can leak out into the calf muscle. This can cause swelling of the calf. You may also develop itching and redness of the skin of your calf because of irritation caused by the fluid that leaks out from the cyst. About 1 or 2 in 20 Baker’s cysts are thought to rupture.

If a Baker’s cyst ruptures, it can be quite difficult to tell the difference between the ruptured cyst and a deep vein thrombosis (DVT) in the leg. A DVT is a blood clot that forms in a leg vein. In these cases, it is important that investigations are carried out to exclude a DVT because it can be a serious condition that needs treatment.

Having a Baker’s cyst can also increase your risk of developing a deep vein thrombosis even if the cyst does not rupture. For this reason, anyone who is found to have a Baker’s cyst should also have a DVT excluded. Similarly, anyone who is found to have a DVT should be examined and investigated for a possible Baker’s cyst.

Very rarely, a Baker’s cyst may become infected.

How is a Baker’s cyst diagnosed?

You would usually present to your doctor with pain behind the knee. On examination the area behind the knee may be swollen.

An ultrasound scan is a good investigation to show a Baker’s cyst and to help to exclude a DVT or popliteal aneurysm at the same time. Sometimes an MRI scan is used to confirm the diagnosis. Again, a Baker’s cyst is often picked up incidentally on a knee MRI.

What is the treatment for a Baker’s cyst?

A Baker’s cyst often gets better and disappears by itself over time. However, it may persist for months or even years before it goes. In a lot of people it causes little in the way of symptoms and no specific treatment is needed.

There are various treatment options that may help if you do have symptoms associated with a Baker’s cyst. These include:

Treatment of any underlying knee problem

  • Support stockings, Non-steroidal anti-inflammatory drugs (NSAIDs), Ice, Crutches, as well as other treatments.

Symptomatic treatment-

There are some other treatment options that are sometimes used:

  • Fluid drainage – with the utilization of an ultrasound device, the cyst can be located very quickly and easily behind the knee. Then under direct visualization with a small needle the cyst can be drained in a few minutes. At the same time some cortisone or PRP can be injected into the joint space to decrease the underlying inflammation that caused the accumulation of fluid.
  • Surgery to remove the cyst – this is sometimes done, especially if a cyst is very large or painful and/or other treatments have not worked. Sometimes a keyhole method is used to close off the connection between the Baker’s cyst and the knee joint. The cyst is also sometimes removed using open surgery. Surgery may be carried out to treat an underlying problem at the same time – for example, repairing a meniscal tear.

To Learn More

If you are interested in learning about a Baker’s cyst aspiration please contact our pain management experts at The Spine and Pain Institute of New York in Manhattan and Staten Island. We would be happy to make an appointment for a consultation and provide additional information about other treatment options.

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