Baker`s cyst: Causes, Symptoms, and Treatment

A knee joint disease causes a Baker’s cyst with chronic knee joint effusion. This results in a bulging (bulge) of the posterior joint capsule, comparable to an overflow valve.

Alternatively, mechanical irritation of the muscles that are located in the hollow of the knee can also cause ganglia (cavities filled with jelly) to form, which are deposited in the hollow of the knee.

A Baker’s cyst occurs particularly frequently in older people due to wear and tear of the knee joint and in children (usually without a clear cause).

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General information

The so-called Baker’s cyst is a bag-shaped fluid-filled sac in the central (medial) popliteal fossa. Its name comes from its first descriptor W. M. Baker an English surgeon of the 19th century from London.

The Baker’s cyst always starts from the knee joint capsule. From the joint capsule, it is connected to the main chamber by a narrow bridge or passage (stem-like connection). In a Baker’s cyst, which is typically located at a normal position, the connecting duct is pushed through the muscular structures of the gastrocnemius muscle (caput mediale) and the semimembranosus muscle (flexor muscles of the thigh). If a Baker’s cyst persists for a more extended period of time, several cyst chambers can form, making puncture of the cyst particularly tricky.

Development of a Baker’s cyst

A Baker’s cyst is often the result of a knee disorder. In the context of rheumatoid arthritis (rheumatism) or chronic meniscus damage, a permanent joint effusion (water in the knee joint) occurs. Due to its swelling nature, a Baker’s cyst can resemble a tumor of the back of the knee, so that a malignant disease must always be ruled out. However, this can quickly be done with a sonographic examination of the popliteal fossa. If an increase in chamber pressure causes the cyst to rupture/tear, i.e., a rupture with leakage of fluid into the tissue, swelling in the affected area, and pain that increases with pressure can be found. This condition can easily be confused with deep vein thrombosis of the leg. If the cause is not eliminated, however, the Baker’s cyst reappears, with uterine chamber formation.

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Causes

The cause for the formation of a Baker’s cyst in the hollow of the knee is the increased production of synovial fluid in the knee joint. The cause of this, in turn, is usually damage to the knee joint, such as osteoarthritis, prolonged meniscus damage, or an underlying inflammatory disease such as rheumatoid arthritis. In the majority of cases, however, the formation of a Baker’s cyst is caused by wear and tear, i.e., arthrosis or a torn meniscus. The knee joint tries to improve the function of the knee joint again by increasing the production of “synovial fluid.” This leads to a permanent increase in the pressure inside the joint. The weakest point of the knee joint capsule gives and gives way and forms the Baker’s cyst. This forms an “overflow sack,” which is connected to the knee joint via a stem-shaped connection. This stem almost always runs between the central (medial) head of the gastrocnemius muscle (calf muscle) and the insertion tendon plate of the flexor muscle. On palpation, a fluid-filled, sealed connective tissue capsule can be palpated in the posterior area of the popliteal fossa, which is particularly tricky in the case of small cysts. For such cases, the ultrasound examination (sonography) is groundbreaking.

Frequency

In principle, a Baker’s cyst can occur at any age. However, children are less frequently affected by the development of cystic changes in the hollow of the knee. If a Baker’s cyst does develop in childhood, boys are affected twice as often as girls.

The disease is predominantly observed in middle and advanced age (typically 60 years and older).

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Symptoms

Patients with a Baker’s cyst report recurrent knee and upper calf pain located on the back of the leg. In some cases, only an uncharacteristic feeling of tension in the hollow of the knee is reported. However, the extent of the complaints depends on the degree of activity of the fluid formation. After exertion, a Baker’s cyst typically swells up considerably and, if left untreated, may no longer be detectable after a few days. Accordingly, the symptoms usually fluctuate with the degree of exertion, corresponding to the tension of the fluid-filled lumen.

Once the Baker’s cyst has reached a specific size, the pain can also occur utterly independent of stress.

In most cases, affected persons feel a feeling of pressure in the hollow of the knee. Depending on the size of the Baker’s cyst, from about 2 cm upwards, it can be felt well in the hollow of the knee. The symptoms also depend on the physical activity. The more active the affected person is, the more pronounced and severe the complaints are. Pain can occur, especially when bending the knee. Besides, severe pain can be provoked by pressure in the hollow of the knee. Depending on the size and displacement of the surrounding tissue, Baker’s cysts can simulate lower leg thromboses by compressing vessels. If the cyst compresses nerves in the hollow of the knee, sensory disturbances such as numbness or paralysis may occur in the lower leg or even in the foot. In addition to palpation, ultrasound, or magnetic resonance imaging can also help to confirm the diagnosis.

If a rupture in the Baker’s cyst occurs in the course of the symptoms, the fluid from the cyst can spread into the surrounding tissue, and the pain becomes worse. Also, the fluid from the cyst may spread to the muscles of the lower leg. This causes an intense inflammatory reaction, which is accompanied by severe pain and swelling. These are symptoms that can resemble deep vein thrombosis. Therefore, it is essential to exclude differential diagnoses such as thrombosis during the closer examination.

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Diagnosis

The diagnosis of a Baker’s cyst can generally be made relatively quickly, if the physician considers this diagnostic option, from a combination of medical history, symptoms, clinical and diagnostic examination. In pronounced forms, the Baker’s cyst protrudes into the hollow of the knee, and medium sizes can usually be palpated in the perfect position. Small Baker’s cysts can usually only be visualized with diagnostic methods.

The following diagnostic methods can help to confirm the diagnosis:

  • An ultrasound examination (sonography) of the popliteal fossa can detect a Baker’s cyst and show its location and size.
  • Conventional x-rays can reveal arthritic changes (wear and tear as the cause of the cyst) in the knee joint.
  • A magnetic resonance imaging (MRI) of the knee can also show the exact anatomical location and the connection to the joint capsule. However, Baker’s cysts sometimes cause diagnostic problems due to unusually bizarre, even very long tubular configurations in bleeding with and without ruptures. An MRI is certainly not necessary for the detection of a classic Baker’s cyst. However, since the cause of a Baker’s cyst must always be treated, the MRI provides helpful additional information about concomitant injuries, such as meniscus tears or the degree of arthrosis.

Therapy

A common form of therapy for Baker’s cysts is physiotherapy.

If the Baker’s cyst does not cause any symptoms, treatment is not necessarily required. If the mobility of the knee is restricted by the cyst or if pain occurs, there is the possibility to undergo conservative therapy on the one hand and surgery on the other hand. This depends on the extent of the swelling and the symptoms it causes.

If symptoms occur, anti-inflammatory drugs such as diclofenac or ibuprofen can be given. In very acute, painful cases, a cortisone injection can also be helpful. However, the method with cortisone is not the method of first choice due to the side effects.

Furthermore, additional measures such as physiotherapy or physical therapies can help to improve the symptoms. However, it is essential to note that the cause of a Baker’s cyst is often an underlying disease of the knee joint, which is accompanied by chronic joint effusions such as cartilage or meniscus damage. For this reason, it is essential to repair the causal damage. If this underlying disease is successfully treated, a Baker’s cyst can regress on its own during therapy.

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Surgery of a Baker’s cyst

If the size of the Baker’s cyst increases and its function is impaired by disturbance of surrounding structures such as blood vessels and nerves, surgery should be considered. In this case, the Baker’s cyst is removed surgically. On the one hand, the cyst can be removed surgically, in which an incision is made in the hollow of the knee, the cyst is freed from surrounding structures and after constriction at the stem of the cyst is eradicated. The joint capsule is then closed. In this way, one tries to avoid recurrences.

Also, it is possible to puncture the cyst and aspirate the fluid. With this procedure, however, the cyst will likely come back, i.e., a relapse will occur.

Besides, the underlying disease should be removed before the cyst is removed, because otherwise there is a possibility that the Baker’s cyst will reappear.

Puncture of a Baker’s cyst

Puncture is an essential part of the treatment options for a Baker’s cyst. The treating physician inserts a needle into the cyst and uses it to remove the fluid contained in the cyst. Besides a purely conservative or surgical therapy, puncture represents a kind of compromise of these strategies. However, it should be noted that puncture is only a treatment for the symptoms of a Baker’s cyst and cannot treat the inflammation, and thus the cause of the cyst’s formation.

For this reason, other therapies are often combined with the puncture of a Baker’s cyst to achieve the best possible treatment success. These therapies aim to prevent the cyst from refilling. For example, anti-inflammatory drugs can be taken, or the deflated cyst can be flushed with cortisone. A bandage that is wrapped around the knee joint can also contribute to a successful treatment. The puncture of a Baker’s cyst is not without complications, and for this reason, should only be performed after an intensive medical consultation. If the puncture is unsuccessful, surgical removal of the cyst may be considered.

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Homeopathy for a Baker’s cyst

In addition to a variety of available therapies for the treatment of a Baker’s cyst, the use of homeopathic remedies is a popular way of treating the cyst in self-treatment. It should be noted that the therapy of Baker’s cyst with homeopathic remedies cannot be recommended from a medical point of view as there is no evidence that the available homeopathic remedies have a healing effect on the cyst. Therefore, the attending physician should always be consulted to explain the individual therapy options and to confirm the safe use of homeopathic remedies, if necessary, with simultaneous conservative or operative therapy.

As a rule, no complications are to be expected when taking homeopathic remedies. Nevertheless, it should be noted that the progression of the disease and the inflammation associated with the Baker’s cyst are given in the absence of therapy and that later treatment may be associated with complications.

Taping

The application of a tape bandage is prevalent for complaints of the knee joint. Especially when it comes to complaints of the muscles or ligaments, the elastic tape can help to increase stability in the knee joint and reduce pain under stress. The Baker’s cyst is usually based on an inflammatory process of the knee joint and cannot be successfully treated by applying an elastic tape dressing alone. Nevertheless, tape bandages can be a useful addition to the therapeutic options of a Baker’s cyst. Whether the use of a Kinesio-tape bandage makes sense in individual cases can be discussed with the treating physician or physiotherapist.

Mainly if the Baker’s cyst has been removed through a puncture or surgery, a Kinesio-tape bandage can prevent the recurrence of a Baker’s cyst. In addition to taking anti-inflammatory medication and a classic physiotherapy with lymph drainage, the bandage can be a useful aftercare measure.

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Forecast

Conservative measures usually only lead to an improvement of the symptoms caused by the Baker’s cyst. A disappearance or “drying up” of the Baker’s cyst is not to be expected when using purely conservative measures. Only an operative therapy of the cause of the excessive water formation in the knee joint (e.g., a meniscus damage) leads to a disappearance of the Baker’s cyst without operating. A direct Baker’s cyst operation leads to the complete removal of the cyst, but a high recurrence rate must be expected after surgery as long as the cause in the knee joint has not been eliminated.

Sport with a Baker’s cyst

The development of a Baker’s cyst is a relatively widespread disease in the population. After the diagnosis of a cyst, many affected persons ask themselves the question of whether there is anything to be said against doing sports while having a Baker’s cyst. It is difficult to make a general recommendation. A Baker’s cyst usually develops based on an inflammatory process in the knee joint. Increased stress on the joint can stimulate these inflammatory processes and can, therefore, not be recommended. This is especially true for large cysts and when pain occurs. In the case of an acutely occurring Baker’s cyst, it is therefore not advisable to participate in particular sports that are associated with a high load on the knee joint (e.g., jogging or individual ball sports).

However, sports that only place a small load on the knee joint may be performed without any problems. Depending on the type of movement, sporting activity can even have a positive influence on the success of treatment for a Baker’s cyst. Exercises that are recommended by a physiotherapist can promote a rapid healing of the cyst during conservative treatment of the Baker’s cyst as well as during operative aftercare.

After the cyst has been treated surgically, the affected knee joint should not be subjected to heavy strain for some time. The treating surgeon can provide the best information about the duration of the sports break.

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Baker’s cyst in a child

The Baker’s cyst can occur at any age, so a Baker’s cyst can also develop spontaneously in a child’s knee joint.

The cause of a baker’s cyst in a child is still unknown, but it is assumed to be a congenital weakness of the joint capsule, which is why the capsule can protrude towards the hollow of the knee if the pressure in the knee joint is too high.

Children are more likely to notice a feeling of tension in the joint than direct pain in the knee. It is also recommended that children have an ultrasound or MRI examination of the knee joint. In this way, differential diagnoses such as hematomas or even tumors of the bones or soft tissues can be ruled out.

In childhood, there is often a spontaneous reduction in the size of the cyst up to the complete disappearance of the cyst. For this reason, it is recommended to wait and see whether the cyst disappears on its own. In case of extreme swelling with restrictions in the knee joint, a puncture of the cyst can be considered. Surgical removal, however, is rarely induced.

It is essential for all parents: Clarify the cause -> if no cause of the Baker’s cyst can be found in the child -> keep calm!

Summary

The Baker’s cyst (popliteal cyst) in the hollow of the knee is a fluid-filled sac in the hollow of the knee. It is an indirect sign of damage to the knee joint.

The damage in the knee joint (the causes of this can be wear and tear, i.e., arthrosis, meniscus damage, or an underlying inflammatory disease, such as rheumatism or rheumatoid arthritis) leads to increased water formation in the knee. The knee joint tries to “lubricate” the knee better but produces too much “joint lubricant” overall. Due to a permanently increased intra-articular pressure caused by increased synovial fluid, the surrounding connective tissue slackens and a fluid-filled cyst forms. The weakest part of the joint capsule, typically the inner hollow of the knee, gives way and forms an “overflow sack” between two muscles.

A Baker’s cyst is a disease of middle to old age (due to increasing wear and tear), although children can also be affected in isolated cases.

Pain and a movement-dependent, frequently recurring swelling in the hollow of the knee and the upper calf muscles are the main features. If the cyst tears (rupture) occur, patients report severe sudden pain in the hollow of the knee. If the cyst has a large volume, swelling in the area of the ankle joint can occur for a short time. In most cases, a new formation of the cyst can be detected after a rupture of the Baker’s cyst.

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