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Swelling in the back of the knee: The Baker cyst

The cause of swelling, pain or an unpleasant feeling of tightness in the back of the knee can in many cases be a so-called Baker’s cyst. A Baker’s cyst, also called a popliteal cyst, is a fluid-filled swelling that forms behind the knee.

Treatment for Baker’s cysts often includes exercises to strengthen the muscles around the affected area, rest and icing of the affected area, and physical therapy. Surgery is necessary in some cases when conservative treatments are not effective. In very rare cases, a Baker’s cyst can rupture and leak joint fluid into other parts of the body, causing additional complications.

In the following post, I’ll explain what exactly a Baker’s cyst is, why it happens, and most importantly, what you can do to reduce the swelling or pain, as well as the tension.


Dr. Martin Gruber während einer OP - Arthroskopie bei Meniskusriss

What is a Baker's cyst?

A Baker’s cyst (named after William Morrant Baker, English surgeon) refers to a cyst in the back of the knee. Strictly speaking, it is a protrusion of the knee joint capsule due to increased intra-articular fluid pressure between the middle portion of the gastrocnemius muscle and the semimembranosus muscle.

What is a cyst?

A cyst is a sac-like pocket of tissue filled with air, fluid, or other material. Cysts can form anywhere in the body and can be caused by infection, tumor growth, or trauma. Depending on their size and location, cysts can cause pain or discomfort. Some cysts are harmless and do not require treatment unless they become infected or cause significant symptoms. Other cysts may need to be surgically removed if they interfere with organ function or put pressure on surrounding organs and tissues. The type of cyst determines which methods are available for its treatment.

Anatomische Darstellung einer Bakerzyste
Älterer Mann mit Arthritis

Who is affected by a Baker's cyst?

A Baker cyst most commonly occurs in adults between the ages of 40 and 70, but can occur at any age. People with arthritis, gout or other inflammatory joint diseases are at higher risk of developing a Baker’s cyst. Women are affected by this disease slightly more often than men. Individuals who engage in strenuous physical activities that involve repetitive motion of the knee are also at increased risk of developing a Baker’s cyst.

Generally speaking, the older you get, the more likely you are to develop a Baker’s cyst, since knee and joint problems increase anyway as you get older. Nevertheless, it is not impossible to suffer from a Baker’s cyst even at a young age.

What are the causes of a Baker's cyst?

Most often, Baker’s cyst formation occurs due to chronic or traumatic meniscal or cartilage damage. In addition to these reasons, wear and tear of the knee joint (gonarthrosis) or diseases of the synovium, such as rheumatoid arthritis and collagenosis, can also be the cause of chronic effusion formation.

Due to the state of irritation, there is constant rubbing in the knee joint, this leads to increased production of synovial fluid in the body and eventually becomes noticeable as a cystic bulge in the back of the knee. Initially, there is a connection between the cyst and the knee joint, but the joint capsule may give way over time with an increase in pressure and form an independent, encapsulated cyst.

Dr. Martin Gruber während einer Knieoperation

Symptoms of a Baker cyst

In many cases, the Baker’s cyst does not cause any pain. However, if it presses on vessels and nerves as the swelling increases, discomfort may result. Therefore, the symptoms usually depend on the size of the cyst and the load on the knee joint.

Affected patients complain of a feeling of pressure in the hollow of the knee, which occurs primarily when the knee joint is bent. Commonly reported complaints include pain in the back of the knee and upper calf muscles, recurrent pressure-sensitive swelling, or, in very large cysts, limited range of motion.

The aforementioned pressure on vessels and nerves can cause numbness (paresthesias) or circulatory problems in the affected leg as a further symptom. The development of thrombosis is also possible, although rare. In the worst case, the Baker’s cyst can burst, leading to sudden onset of severe pain of the knee joint or the entire lower leg. In this case, severe swelling and inflammation of the affected leg can lead to the formation of a compartment syndrome.

With immobilization, however, the symptoms can also quickly recede or even disappear completely.


Are you looking for a knee specialist to treat a Baker cyst? Visit me in my practice at MZA – together we will find the most suitable therapy solution for you!

Diagnosis of a Baker cyst

The scope of an accurate diagnosis is the recording of the course of the disease in the course of a careful anamnesis including any previous diseases, as well as a clinical examination of the affected knee joint. A Baker’s cyst can be palpated from a size of about two centimeters in the medial popliteal area. Swelling may decrease flexion in the knee joint when compared laterally. Additionally, signs of thrombosis or signs of numbness are possible.

In addition to clinical manual examination, the diagnosis can be confirmed by ultrasound (sonography) or magnetic resonance imaging (MRI). Sonographically, there is an anechoic space with posterior acoustic enhancement. MRI helps to visualize the exact size and extent of the Baker’s cyst and also provides information about possible causes of its development, such as meniscus or cartilage damage.

Dr. Martin Gruber während der Operation einer Baker-Zyste

Therapy and treatment options of a Baker cyst

The treatment of Baker’s cyst covers a range of options, from surgical to conservative approaches. Baker’s cysts, which do not cause any symptoms and are often discovered as an incidental finding, do not require specific therapy. In general, treatment of a Baker’s cyst should focus on treating the underlying disease or cause of its development.

Conservative therapy

In many cases, the Baker’s cyst already regresses after the knee joint has been rested. Conservative treatment options in addition to immobilization may include analgesic and anti-inflammatory medications, as well as physical therapy. Puncture of the Baker’s cyst is possible, but often brings only a short-term improvement in symptoms and carries the risk of new development.

Most important is treatment of the underlying cause of the Baker’s cyst, such as possible meniscal or cartilage damage. In many cases, these can be remedied by arthroscopy. After repair of the damage in the joint, regression of the cyst occurs in most cases.

Mann während einer Physiotherapie-Behandlung

Treatment through surgery

If the symptoms of the cyst in the popliteal fossa are pronounced and persistent, it can be surgically removed. However, this is rarely successful arthroscopically; in most cases, an open procedure is required. The Baker’s cyst is exposed to the junction with the joint capsule and removed in its entirety.

A Baker’s cyst is often discovered as an incidental finding and remains asymptomatic. Occasionally, however, swelling, pain, and restricted movement may occur, including possible complications. It is then important to determine the exact cause of the development and subsequently initiate appropriate treatment options.

As a knee specialist, I am always available to help you diagnose and treat a Baker’s cyst if you have any complaints.

Dr. Martin Gruber während einer Knieoperation

Do you need a specialist to support you in the treatment of various knee problems?

I am a sports orthopaedist and knee specialist, Dr Martin Gruber, and I get to the bottom of every swelling, every pain and every restriction of mobility to help you lead a pain-free life. During my work as a doctor, I have already cured various knee diseases and therefore know what is important!

Would you like to get to know more about your knee problems? Contact me by phone, at the e-mail address or make an appointment directly online.

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