A Baker's cyst is a bulge filled with synovial fluid in the joint capsule of the knee joint in the hollow of the knee. This is caused by increased production of joint fluid as a result of knee osteoarthritis or damage to the meniscus. A palpable bulge and a feeling of tension or pain in the hollow of the knee are typical signs of a Baker's cyst.

An overview of Baker’s cysts

A Baker's cyst, also known medically as a popliteal cyst, is a swelling filled with joint fluid in the joint capsule of the hollow of the knee. It occurs when excess fluid leaks into a bursa in the hollow of the knee and a cyst forms. The bulge in the affected joint is usually soft and elastic and may increase in size when the knee is moved. In some cases, it becomes so large that it can be clearly seen or felt.


A Baker's cyst usually indicates an underlying disease or damage to the knee joint and occurs predominantly in middle and old age. Potential triggers include:

  • Meniscus damage
  • Cruciate ligament rupture
  • Knee osteoarthritis
  • Rheumatic diseases

The injuries or underlying diseases listed lead to the formation of excessive fluid in the knee. This increases the pressure in the knee joint and can lead to the joint capsule protruding into the hollow of the knee.

Disease progression

The disease progression of a Baker's cyst varies depending on the size of the cyst and its underlying cause. In the majority of patients, the Baker's cyst forms slowly over a long period of time and usually causes mild to moderate symptoms such as swelling, pain or a feeling of tension in the hollow of the knee. The symptoms may vary over time and may either increase or decrease. The cyst, however, can also suddenly become larger or inflamed, and in rare cases even burst, leading to severe pain and swelling in the knee.


The symptoms of a Baker's cyst can vary depending on the size of the cyst. Smaller cysts often cause little or no discomfort to the affected joint and may go unnoticed. Larger ones, however, can be externally visible and palpable. They can be associated with a feeling of tension, pain and stiffness in the knee or calf.

Bulges or pain in the hollow of the knee should always be checked by an orthopaedic specialist because in addition to a benign cyst, they may also indicate other serious diseases such as venous thrombosis or a malignant tumour in the knee area.


A Baker's cyst can often be diagnosed on the basis of the characteristic bulge in the hollow of the knee and the associated symptoms. In order to obtain a more precise assessment of the size and location of the cyst, an ultrasound examination is usually performed. Because the Baker's cyst is often the result of damage to the knee joint or chronic inflammation, a thorough examination of the entire knee is also performed. X-ray images or MRI examinations may also be used within this process.


As with the disease progression and the symptoms, the treatment of a Baker's cyst also depends on the size of the cyst and the extent of the patient's symptoms.

Small to medium-sized Baker's cysts without severe symptoms

Often in the case of small Baker's cysts, the change in the affected knee is observed and the symptoms are alleviated with conservative therapy.


Regular check-ups can help to monitor changes in the cyst.

Conservative treatment

Painkillers and anti-inflammatory drugs can be used to alleviate the symptoms.

Larger Baker's cysts with severe symptoms

Larger or recurring Baker's cysts may require a puncture or surgery to remove the cyst.

Puncturing of the cyst

When a cyst is punctured, the accumulated fluid is drained and the pressure on the knee joint is reduced.

Surgical removal

In the case of recurring cysts or if there is no improvement over a longer period of time, an operation to remove the Baker's cyst is recommended.

Treating the underlying cause

Because Baker's cysts often develop as a reaction to damage to the knee or a joint disease, it is important to treat the underlying cause. This may include the following measures:

Torn meniscus

If an injury to the meniscus is responsible for the Baker's cyst, the meniscus damage must be treated accordingly. You can find out more about this in the section on knee arthroscopy

Cruciate ligament rupture

If a cruciate ligament rupture has caused the formation of the Baker’s cyst, appropriate treatment of the cruciate ligament is necessary. Should surgical intervention be necessary, the procedure is usually performed arthroscopically. You can find out more about this in the section on knee arthroscopy.

Osteoarthritis of the knee joint

If knee osteoarthritis is responsible for the development of the Baker's cyst, non-surgical treatment, arthroscopy, or joint replacement may be considered, depending on the stage of the osteoarthritis. You can find out more about this in the section on knee replacement.

Rheumatic diseases

The Baker's cyst can also be caused by a rheumatic disease. You can find out more about rheumatic diseases in the section on rheumatology.


Preventing a Baker's cyst can be difficult, as it is usually the result of other joint diseases or injuries. Generally, the following measures can reduce the risk of the formation of Baker's cysts:

  • Regular exercise
  • Exercises to strengthen the knee muscles
  • Avoidance of knee injuries
  • Early treatment of joint diseases
  •  Weight control
  • Physiotherapy on the first signs of knee pain or injury
  • Avoidance of excessive strain on the knees

Centres 5