What is A Bakers Cyst

What is A Bakers Cyst

Baker’s cyst is a fluid-filled sac that forms behind the knee; for this reason, it is also known as a popliteal cyst. Damage to the knee joint often determines its formation. So, in this article, we will give you a complete guide about what is a bakers cyst.

The presence of a Baker’s cyst is, in some cases, asymptomatic; in others, however, it causes pain, swelling, and a sensation of joint stiffness. In the most serious patients, the leakage of the cyst’s liquid inside should not be excluded. So according to the causes that lead to a Baker’s cyst formation, different therapeutic measures are applied, more or less invasive.

Review of the anatomy of the knee       

To understand what Baker’s cyst is, a brief review of the knee joint should be done. The knee joint is placed between the femur and tibia. It is made up of several elements, all equally important in allowing movement and supporting the human body’s weight. The synovial fluid acts as a lubricant: it avoids rubbing between the femur and tibia cartilages and facilitates the movement of the tendons and ligaments of the knee. The latter is fundamental: they allow the movement of the leg and, at the same time, give stability to the joint.

Their function is to reduce friction between ligaments and tendons. The anterior ones are two: pre-patellar bursa and infra-patellar bursa. Finally, the menisci are missing: lateral and medial. They occupy the upper part of the tibia and absorb the stresses that the femur and upper body exert on the tibia itself. In other words, they provide stability.

What is Bakers cyst?

The Baker’s cysts (or popliteal cyst ) are presented as a lump behind the knee, similar to a nut and visible to the naked eye; the formation of this sac is due to the synovial accumulation fluid leaking from the popliteal bursa.

The precise area of ​​onset of the cyst is that which connects the thigh’s semimembranous muscle and the gastrocnemius of the calf.


The size of a cyst can vary: in some cases, it is small; in others, it is very large (even several centimeters). Also, more than one cyst is likely to form behind the knee.


Baker’s cyst comes from Dr. William Baker, who was the first to describe this condition in 1877.

EPIDEMIOLOGY: What is A Bakers Cyst

Baker’s cyst occurs mainly in adults between the ages of 35 and 70. This is because in this age group, other joint disorders of the knee (for example, arthritis), which favor the leakage of synovial fluid, are more common. 

What is a bakers cyst Causes?

The causes of Baker’s cyst are essentially two: it can have an idiopathic origin (the so-called primary Baker’s cyst) or be a direct consequence of another joint disease of the knee; in the latter case, we speak of secondary Baker’s cyst.


Primary Baker cysts are typical of young age (4-7 years) and occur without a precise reason (idiopathic origin), as the knee joint is healthy. 


The cyst’s secondary Baker is typical of ‘ adulthood (35-70 years). Its formation is a direct consequence of a pre-existing pathology of the knee; in fact, a Baker’s cyst hardly forms in a healthy knee.

When a knee has a disorder, such as arthritis or a meniscal tear, it produces more synovial fluid. This is a physiological response, which serves to safeguard the health of the knee. However, the accumulation of fluid causes an increase in pressure within the joint capsule, which pushes the same fluid into the popliteal bursa forming the cyst.

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Several diseases associated with Baker’s cyst have been identified; the following table summarizes the main ones.

  • Associated diseases, predisposing to Baker’s cyst
  • Osteoarthritis
  • Rheumatoid arthritis
  • Psoriatic arthritis
  • Septic arthritis
  • Osteochondrosisdissecans
  • Gout
  • Meniscal injuries
  • Injuries of the ligaments

What are a baker’s cyst Symptoms and complications?

The main symptom of Baker’s cyst is the appearance of a lump-like mass in the back of the knee, which is hard under direct pressure.

The general symptom picture is as follows:

  • The appearance of a lump-like mass in the back of the knee
  • Swollen knee
  • Pain in the knee, which radiates to the calf
  • Joint stiffness
  • Noise (click) to the movement of the knee

These symptoms present to varying degrees based on the severity of any pre-existing joint disorder. Although rare, some patients may not experience the symptoms above. 

COMPLICATIONS: What is A Bakers Cyst

The most common complication (about 1-2 in 20 people) of Baker’s cyst is the rupture of the cyst’s synovial membrane, with the consequent leakage of the fluid contained therein. When this occurs, synovial fluid invades the calf’s gastrocnemius muscle; in response, the latter will develop a bump, visible to the naked eye, sometimes red and itchy.

The rupture of the cyst resembles, in some respects, the so-called deep vein thrombosis (or thrombophlebitis). So it is essential to recognize the two circumstances in such situations, as thrombophlebitis is much more dangerous and requires specific treatment. What is a bakers cyst can also undergo other complications, much rarer than the previous one. The table summarizes them:

Baker’s cyst: what complications are possible?

  • Rupture of the cyst and consequent leakage of synovial fluid
  • Hemorrhage in patients with a predisposition to bleeding (hemophilia)
  • Infections due to Streptococcus pneumonia, Candida albicans, brucellosis, and tuberculosis
  • Calcification of the cyst
  • The pressure of the cyst to damage the peroneal and tibial nerve

Diagnosis: What is A Bakers Cyst

Observing a lump located behind the knee is the first step towards a correct diagnosis. 

However, if doubts remain or the cyst is not recognizable with the naked eye, two instrumental tests can be used, such as:

  • Ultrasound
  • Nuclear magnetic resonance

These procedures are also reliable in terms of differential diagnosis to exclude other pathologies with similar symptoms.

Doctors use ultrasound to check whether it is a Baker’s cyst or a solid mass of another nature. The ultrasound examination allows to evaluate the swollen area’s internal structures: a cyst has specific elements, and its identification excludes the possibility that it is a deep vein thrombosis.


It allows precise localization of the cyst and an even more accurate description of its internal characteristics.


Baker’s cyst has symptoms very similar to other more serious pathologies. Therefore, it is good to ascertain the true cause of these symptoms by subjecting the patient to the diagnostic tests listed above. But what are these pathologies that can be confused with a Baker’s cyst?

  • Deep vein thrombosis
  • Hemangioma
  • Hemophilic arthroplasty
  • Benign soft tissue neoplasms (nerves, in particular)
  • Malignant neoplasms: lip sarcomas (in adults), lipoblastomas (in children), lymphangiosarcoma, Kaposi’s sarcoma
  • Meniscal cysts
  • Ganglion cysts
  • Injury of the gastrocnemius muscle of the calf

Baker’s cyst treatment

For the successful treatment of this disease, depending on the size and duration of Baker’s cyst, methods of conservative and surgical therapy can be used. Conservative therapy for Baker’s cyst usually consists of puncture (to remove synovial fluid) and subsequent drug administration of glucocorticosteroid and nonsteroidal anti-inflammatory drugs, painkillers into the intertendinous bag.

Surgical therapy for Baker’s cyst is indicated in the absence of an effect from conservative treatment methods and large sizes of the formation and its pronounced destructive effect on the surrounding tissues. The excision operation is performed using local anesthesia. Also, recently, the removal of Baker’s cyst with the help of an arthroscope has been very much in demand, which is less traumatic for the patient, since the outflow of synovial fluid is performed through a mini-puncture and at the same time, the contents of the cyst from entering the joint cavity are completely excluded.

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What is a bakers cyst Therapy?

As long as Baker’s cyst is not causing any particular symptoms or ailments, no treatment is needed. Often, this asymptomatic condition remains stable, and the cyst resorbs spontaneously, without any intervention. However, patients with arthritis or other disorders predispose to cyst formation need treatment, as the situation tends to escalate. It is unrealistic to think of spontaneous improvement in such circumstances: for example, rupture of a meniscus or ligament does not heal spontaneously but requires surgery.

In these cases, therefore, Baker’s cyst therapy has two objectives:

  • Limit the joint damage of the knee, which indirectly causes the cyst
  • Relieving specific symptoms of Baker’s cyst

Finally, if the cyst becomes very large and the pain becomes unbearable, surgery must be done.


As mentioned, damage to the knee joint, developed over the years, favors Baker’s cyst formation. Remedying these joint disorders, while not representing a specific cure for Baker’s cyst, helps slow down the cyst’s degeneration itself. For example, it is very useful to apply countermeasures that reduce inflammation and the overproduction of synovial fluid.

Therefore, we act in the following way:

  • Injection of corticosteroids to reduce inflammation.
  • Aspiration of synovial fluid, directly from the cyst
  • Rest and lower limb raised
  • Specific arthroscopic treatment of underlying arthritis and meniscal and ligament injuries.


Different treatments can be applied to alleviate the pain and possible expansion of Baker’s cyst.

Compression stockings or bandages.

Purpose: they reduce swelling, the risk of rupture of the cyst, and the effects that this event could cause.

Nonsteroidal anti-inflammatory drugs (NSAIDs).

Purpose: They reduce inflammation and limit pain.

Side effects: possibility of gastric bleeding, ulceration, nausea, and vomiting.

Contraindications: for those who have asthma, hypertension, and renal and heart failure.

Ice: What is A Bakers Cyst

Purpose: reduces swelling and pain.

Application: the ice pack should be kept on the affected area for 15-30 minutes and should be repeated several times a day. Less than a quarter of an hour has little effect; more than half an hour damages the skin.


Purpose: they reduce the weight on the affected limb. Excessive weight can cause a stressful situation for the knee, favoring the formation of additional synovial fluid.


  • If it becomes large and the pain becomes unbearable, the patient must undergo surgery.
  • There are two possibilities of intervention.
  • The first, less invasive method is arthroscopy.
  • The second method is the excision of the anatomical portion occupied by Baker’s cyst. It is a more invasive approach than the first.

How dangerous is Baker’s cyst

The main danger of Baker’s cyst (in the absence of timely and effective treatment) is associated with its complications, which can manifest themselves:

  • its rupture (the most frequent complication, characteristic of almost 10% of patients with this ailment) – while the synovial fluid of the cyst penetrates the nearby gastrocnemius muscle, filling the space between its fasciae, which contributes to the formation of edema in the lower leg, which is often accompanied by general discomfort with pain, local hyperthermia, and skin redness;
  • deposition of calcium salts in the cyst – with a more noticeable pressure of the compacted formation on the surrounding tissues;
  • violation of venous circulation – the presence of a cyst often interferes with the normal venous outflow in the leg, which, in turn, leads to the development of thrombophlebitis and thrombosis in the veins of the leg (which can be complicated by the life-threatening patient with pulmonary embolism);
  • varicose veins located under the skin of the lower leg;
  • compression of the tibial nerve – due to which the patient begins to experience a feeling of numbness or tingling (sometimes just weakness) in the lower leg;
  • necrosis – due to compression of soft tissues;
  • osteomyelitis – due to compression of the bone and its further suppuration.


The prognosis for a patient with one or more Baker’s cysts depends on several factors. For example, a young individual, or even a child, can recover without resorting to special care. Therefore, in these cases, the prognosis is more than positive.

An adult, on the other hand, especially if elderly or with knee joint disorders, needs treatment, including surgical treatment. The prognosis, therefore, becomes worse.

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