Baker’s cysts

In adults, Baker’s cysts are often caused by injuries or wear and tear on the knees. They can cause mild pain and feelings of tightness. In most cases, the cysts clear up on their own without treatment.

At a glance

  • A Baker’s cyst occurs when excess fluid accumulates at the back of the knee.
  • It can cause mild pain and feelings of tightness.
  • In adults, the cysts are usually caused by injuries, wear and tear on the knees (osteoarthritis) or chronic inflammatory joint diseases.
  • Anyone with a Baker’s cyst should avoid putting excessive strain on the knee.
  • In many cases, smaller cysts clear up on their own without treatment.
  • Cooling and stretching the knee may relieve the pain.

Note: The information in this article cannot and should not replace a medical consultation and must not be used for self-diagnosis or treatment.

Woman in white work clothing holding the knee of a man sitting on a treatment chair.

What is a Baker’s cyst?

When a Baker’s cyst occurs, fluid builds up at the back of the knee, causing a swelling.

The upper and lower leg bones meet at the knee joint. Between them is the narrow joint cavity. To keep the joint working smoothly, the cavity is filled with a fluid known as synovial fluid. The joint and joint cavity are surrounded by the joint capsule, which also contains cushioning sacs of fluid that are called bursae.

When a Baker’s cyst occurs, excess synovial fluid builds up in a bursa. The fluid often breaks through into the joint capsule and appears as a swelling at the back of the knee.

In adults, Baker’s cysts usually occur due to an injury or an inflammation in the knee joint. Depending on the size of the cyst, it may frequently be accompanied by a feeling of tightness or pain in the knee.

Small Baker’s cysts often go unnoticed and clear up on their own without treatment. Treatment is necessary if symptoms develop.

Baker’s cysts occur most frequently in women and men aged between 35 and 70.

What are the symptoms of Baker’s cysts?

Small Baker’s cysts often go unnoticed and cause no pain.

Larger cysts may cause the following symptoms:

  • feelings of stiffness and tightness behind the knee
  • pain in and behind the knee
  • stiffness in the knee joint
  • swelling at the back of the knee
  • swollen calf

In addition, pain is often worse if the knee is moved a lot.

What causes Baker’s cysts?

In adults, Baker’s cysts often develop after a knee injury, such as a torn meniscus, or as a result of a chronic joint disease, such as rheumatoid arthritis, gout or osteoarthritis.

Baker’s cysts in adults often develop after a knee injury.

Fluid from the joint cavity can flow or be squeezed through fine cracks into a bursa. The enlarged bursa becomes distended and appears as a swelling at the back of the knee.

Which factors increase the risk of developing a Baker’s cyst?

The stability of the knee capsule declines with age. Frequent exertion or excessive strain can cause tiny cracks in the capsule. This, in turn, enables an exchange of fluid between the joint cavity and bursae in the knee capsule – increasing the risk of Baker’s cysts developing.

Older adults are also more likely to have suffered a knee injury at some point in their lives. Chronic joint diseases are also more likely to occur with age. Both of these factors increase the risk of developing a Baker’s cyst.

What are the possible complications of a Baker’s cyst?

If a large volume of fluid builds up in a Baker’s cyst, it presses on the surrounding blood vessels. The cysts may also extend into the calf. In both cases, redness, fluid retention and swelling in the legs may occur.

Baker’s cysts occasionally burst. If the synovial fluid from the cyst flows into the surrounding tissue, it may cause inflammation. This causes sharp pain, swelling and skin discoloration. If nerves in the legs are affected, this may cause feelings of numbness and calf pain.

While the pain generally disappears after a few days, the swelling and restricted movement in the knee may last for longer.

How is a Baker’s cyst diagnosed?

A Baker’s cyst is most clearly visible when the affected leg is stretched out. The doctor can then see and feel the solid bulge where the fluid has accumulated. When the knee is bent, pressure is taken off the cyst and so it becomes softer or may even disappear entirely.

Further tests are required if the diagnosis is not clear. In these cases, doctors will use imaging techniques, such as:

  • ultrasound
  • magnetic resonance imaging (MRI)
  • X-ray

These techniques make it easier to detect changes in joints or tissue, for example. Small cysts are also easier to see on an ultrasound scan.

How are Baker’s cysts treated?

Baker’s cysts are only treated if symptoms develop. It is important to avoid placing stress on the knee for a while.

Treatment is only needed for baker’s cysts (popliteal cysts) if they cause problems.

Anti-inflammatory pain medication and physiotherapy may also help. The goal of physiotherapy is to keep th knee mobile and to stabilize it. This is achieved through targeted training of the leg muscles.

  • AIM Speciality Health. Clinical Appropriateness Guidelines: Avanced Imaging, Appropriate Use Criteria: Imaging of the Extremeties. Reaffirmed version July 08, 2020.
  • DynaMed [Internet], Ipswich (MA). Popliteal Cyst. EBSCO Information Services. Record No. T116564. 2018 (1995). Aufgerufen am 28.05.2021.
  • UpToDate (Internet). Popliteal (Baker's) cyst. Wolters Kluwer 2019. Aufgerufen am 28.05.2021.
  • Leib AD, Roshan A, Foris LA, Varacallo M. Baker's Cyst. [Updated 2020 July 17]. In: StatPearls [Internet]. Treasure Island (FL). StatPearls Publishing; 2021 Jan-. Aufgerufen am 28.05.2021.

In cooperation with the Institute for Quality and Efficiency in Health Care (Institut für Qualität und Wirtschaftlichkeit im Gesundheitswesen – IQWiG).

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