Baker's Cyst - Popliteal Cyst

The Baker's cyst, also known as popliteal cyst, is a small net bag that arises in the region behind the knee, called popliteal fossa.

Bakers cyst
Bakers cyst

The Baker's cyst is a benign lesion that appears as a visible and palpable lump under the skin and can cause knee pain and difficulty moving this joint. When the cyst is small, it can be asymptomatic, unnoticed by the patient.

In this article we will explain what the Baker cyst, why it arises, what are its symptoms and how it is done the treatment.

What is Baker's cyst?

In medicine we call all cyst fluid collection or semi-liquid which is surrounded by a membrane, forming a kind of pouch or bag.

Baker's cysts (popliteal cyst) arises when there is an extravasation in the synovial fluid of the knee joint. Synovial fluid is a kind of lubricant, whose main function is to reduce friction during movement of joints such as the knee.

When an injury of the knee joint or when the amount of synovial fluid becomes excessive, it can be compressed and pushed into the posterior region of the joint, forming a herniation, as shown in the figure.

Causes of Baker's cyst

As just said, the popliteal cyst arises when there is a knee injury and / or when the volume of liquid inside the joint becomes very large.

Generally, knee trauma and inflammatory joint diseases, such as various forms of arthritis are the main risk factors.

Examples of commonly related situations to the formation of Baker's cyst, we can mention osteoarthritis, rheumatoid arthritis, infectious arthritis, juvenile arthritis and various types trauma of the knee, especially if there is damage to menisci.

Symptoms of Baker's cyst

Most popliteal cysts are asymptomatic and invisible to the physical examination and end therefore being discovered by chance during the course of a knee imaging, such as MRI, requested for any other reason.

In general, Baker's cysts adults is a change, occurring with greater frequency from 35 years of age. As the individual grows older, more worn becomes the articulation of their knees and the greater the incidence of popliteal cyst.

The occurrence of symptoms Baker's cyst depends on some factors such as its size or the existence of complications such as excessive growth or rupture of the cyst.

When symptoms do occur, the most common are pain in the popliteal fossa (back of knee) of the knee joint stiffness, swelling and appearance of a palpable nodule behind the knee, particularly when the same if it is found in length, or with the fully extended leg. These signs and symptoms may worsen with physical activity.

Complications of popliteal cyst

The popliteal cyst can grow much or break, causing a frame that can be confused with deep vein thrombosis of the lower limbs.

A cyst that grows much can cause pain and swelling of the leg, especially if compression of adjacent veins, disrupting the flow of blood from the lower limbs.

When cyst ruptures, this liquid runs through the muscles, causing an inflammatory reaction. The picture is pain, redness and swelling in the calf region.

The Baker's cyst is a kind and cancer?

No, Baker's cyst has nothing to do with cancer. This cyst is a benign tumor composed primarily of liquid. The popliteal cyst is not cancer and have no risk of becoming cancer.

Diagnosis of Baker's cyst

Physical examination usually sufficient for diagnosis of the majority of Baker's cysts that are large enough to be visible.

When in doubt, or if the cyst is too small, imaging tests, such as ultrasound and magnetic resonance imaging can be used. The resonance is also used to evaluate the knee joint as a whole, supporting the diagnosis of the injury that led to the formation of the popliteal cyst.

Treatment of Baker's cyst

In asymptomatic patients with small cysts, no treatment is necessary since most spontaneously disappears with time.

When the cysts are too large or causes symptoms, initial treatment is usually a knee arthroscopy, to drain the excess fluid within the joint and intraarticular injection of a glucocorticoid, such as triamcinolone. With this treatment, within a week, about 2/3 of the patients present a significant reduction of symptoms and cyst size.

The primary treatment of knee injury is essential to reduce the risk of return of the cysts in the future. Do not just treat the cyst, you need to control your question.

If there is no improvement, the orthopedist can, through a needle, aspirate the cyst directly injecting steroids then to reduce the risk of recurrence. This procedure is not the most appropriate, first because the liquid of the cyst is usually very viscous, not easy to be sucked by a needle; second, because this form does not address the knee injury and thus does not attack the cause of cyst formation, there is therefore a high risk of recurrence.

In the rare cases where treatment with arthroscopy and knee inflammation control are not enough to solve the popliteal cyst, surgery to remove the same can be proposed.

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