A Baker’s cyst also known as a popliteal cyst arises from the knee joint and causes lumps at the back of the knee. A bakers cyst drainage is sometimes necessary to remove pressure from the back of the knee. Is a bakers cyst drainage necessary?

What is a Bakers cyst? 

A Bakers cyst is a fluid-filled sac. It forms when excess knee fluid pushes the back part of the knee capsule outwards. This forms a sac of fluid called a cyst. This cyst is also called a ‘popliteal cyst’ as it forms in the popliteal area of the knee.

baker's cyst


A Baker’s cyst forms due to excessive fluid build-up in the knee. Usually, excess fluid is produced in conditions such as osteoarthritis, rheumatoid arthritis, and a torn meniscus.

In general, it is important to make sure that the lump in the back of the knee is not due to other pathology. More serious conditions that can look like a simple cyst include tumours, blood clots, and swollen arteries (also called aneurysms).  Often, imaging such as an ultrasound or MRI can spot a simple cyst from more serious causes.

What are the symptoms of a Bakers cyst? 

Often, a Bakers cyst is symptom-free. The only noticeable change is a palpable soft lump at the back of your knee. Sometimes, the cyst can become tight or painful particularly when straightening the knee.

The cyst can increase or decrease in size depending on how much knee joint fluid is produced.

In some cases, the cyst might burst to produce redness, warmth, and swelling of the calf. A ruptured Bakers cyst is often confused with a blood clot. In cases of calf swelling, it is important you see your doctor to exclude a blood clot. In many cases, an ultrasound or a blood test will be needed.

Bakers cyst vs ganglion cyst: how to tell the difference 

A ganglion cyst also called a meniscal cyst comes from a meniscal tear. These cysts form on the inside or the outside of the knee. However, sometimes, the cyst can develop at the back of the knee and can mimic a Bakers cyst. Generally, an ultrasound is useful to determine whether the swelling at the back of the knee is a Bakers cyst or a meniscal cyst. The picture below shows a deep ganglion cyst coming from the meniscus in the joint.

ganglion cyst at back of the knee on ultrasound

What to do for a Bakers cyst including Bakers cyst drainage

In general, treatment options depend on the cause, but nearly all cases should be managed non-surgically.

These options include:

  • ice to the swollen cyst and knee joint
  • oral anti-inflammatory tablets
  • compression of the knee joint using a compression bandage
  • drainage of the cyst using a needle and syringe
  • treatment of the cause of the excess swelling. For example, treatment of arthritis with exercise therapy can reduce the swelling produced by the joint and therefore the cyst.

Finally, surgery should be avoided unless the cyst fails to settle with simple treatments or becomes painful or bothersome. However, even after removal, the cyst can come back.

Popliteal cyst aspiration technique

A Bakers cyst drainage is appropriate for cysts that get bigger or more painful despite simple treatments. It is important to get imaging such as an ultrasound to confirm a simple cyst. Also, ultrasound allows you to insert the needle in the right spot and drain the entire cyst. Often the needle is inserted into the middle of the cyst to make sure most of the fluid is removed. In some cases, an injection of cortisone into the sac prevents the cyst from coming back. In addition, if excess fluid is produced by arthritis or a torn meniscus, some doctors inject a small dose of cortisone into the joint at the same time.

Infected Baker’s cyst: is it possible? 

Infected Baker’s cyst is rare. Nevertheless, you need to think about an infected Baker’s cyst if you develop swelling and pain at the back of the knee.

What happens when a Bakers cyst ruptures? 

baker's cyst rupture

Sometimes, swelling in the Baker’s cyst increases and ruptures. So, fluid from the cyst leaks into the calf causing calf swelling. Often, the cause of swelling is misdiagnosed as a more serious blood clot. It is important that an ultrasound is performed to confirm a ruptured cyst and rule out a blood clot.

Thankfully, a baker’s cyst rupture is harmless and does not need special treatment apart from leg elevation and compression of the calf.

Ruptured bakers cyst vs DVT 

Often, it can be difficult to differentiate between these two conditions. While a baker’s cyst is harmless, a DVT can be life-threatening. Generally, an ultrasound is an easy way to get an accurate diagnosis.

Final word from Sportdoctorlondon

If you’re unsure about a lump behind the knee, I suggest you see your doctor. Ultrasound is an easy way to confirm a Bakers cyst and rule out other lumps. At Sportdoctorlondon, we will often perform a Bakers cyst drainage using ultrasound. Also, we may inject the knee joint at the same time if there is excess joint fluid.

Other knee conditions:

Dr. Masci is a specialist sport doctor in London. 

He specialises in muscle, tendon and joint injuries.

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