What is a popliteal cyst?
A popliteal cyst, also called a Baker's cyst, is a cavity filled with synovial fluid in the hollow of the knee, the so-called fossa poplitea. The condition can develop in young children and often affects both knees at the same time. In adults, on the other hand, a popliteal cyst usually occurs on one side of the knee and suggests that a joint pathology is present.
How does a popliteal cyst develop?
A popliteal cyst is often caused by an internal knee disease that secretes excess synovial fluid. Internal knee disease can have several causes, such as:
- an inflammation of the knee, such as rheumatoid arthritis,
- a chronic meniscus injury,
- quadriceps muscle insufficiency,
- a joint injury, such as a ligament or meniscus injury,
- osteoarthritis.
The internal knee disease causes a constant increase in internal pressure, which is largely responsible for the bulge in the form of the popliteal cyst.
What symptoms does a popliteal cyst cause?
Depending on its size, the popliteal cyst reacts sensitively to pressure and can be felt as a spherical, bulging, elastic bulge in the knee joint. The popliteal cyst can be about the size of a tennis ball and appears larger when the knee is extended. A popliteal cyst can affect knee flexion, but also walking and squatting. It often causes pain due to its extension to the adjacent muscle insertions and may even manifest as tingling or burning in the calf.
How is a popliteal cyst diagnosed?
A popliteal cyst is not palpable in every case. In some cases it is rather small and asymptomatic, which is why it is discovered as an incidental finding. If a popliteal cyst is suspected, however, the diagnosis can be confirmed by an MRI examination. X-rays, together with ultrasound examinations, can be used to check whether a joint pathology is present. In any case, the popliteal cyst should be examined to see if it is not a malignant tumour. It is advisable to prove that the cyst is benign.
How is a popliteal cyst treated?
If the popliteal cyst has occurred in children, surgery is rarely necessary. In adults, too, it can be assumed that the cyst will disappear over time, provided that the internal knee disease has been treated successfully. However, if the popliteal cyst causes great discomfort or has reached a certain size, surgery may be advisable. However, even with surgery, the treatment of the underlying pathology should not be neglected, otherwise the popliteal cyst will form again.
As an alternative to surgery and depending on the size of the popliteal cyst, the condition can also be treated by puncture. Treatment with cortisone is also possible, which should dry out the popliteal cyst.