Baker's Cyst
A Baker's cyst or popliteal cyst is a structure located at the back of the knee. This cyst occurs due to a distension of the popliteal bursa, a kind of bag located between the tendon of the semimembranosus muscle and the inner part of the gastrocnemius muscle (one of the calf muscles).
Despite being outside the knee joint, Baker's cyst communicates to the joint. Thus, intra-articular inflammation that cause knee effusion can increase the volume of the cyst. Often, the fluid accumulated inside the cyst cannot go back to the joint due to a valve mechanism. Baker's cysts are found in 5 to 19% of knee MRIs. The incidence increases in the elderly population. Usually, the cyst is associated with some intra-articular disorder, such as meniscal injury, ligament injury and osteoarthritis.
What the Patient Feels
Patients with a Baker's cyst may feel pain in the back of the knee and swelling in the area. When the cyst ruptures, this pain may be more intense and there may be affusion in the back of the knee and in the calf. In these cases, the doctor should be vigilant, as the patient's condition may be confused with more serious situations, such as venous thromboembolism.
Knee pain secondary to a Baker's cyst may be related to the underlying injury that causes the inflammatory process in the knee, such as osteoarthritis, cartilage or meniscus tears, among others.
Imaging Exams
Some imaging tests can help the doctor when there is a suspicion of a Baker's cyst. Ultrasound and magnetic resonance imaging of the knee are the main tests requested. It is important to note that these exams are important for diagnosing injuries associated with a Baker's cyst, since they are directly related to the symptoms.
Treatment
In most cases, treatment for Baker's cysts is non-surgical and patients are treated with medication and physical therapy. In some cases, some type of surgical procedure may be necessary, which is usually performed by video (arthroscopy) and is mainly based on the treatment of associated injuries, such as meniscus, ligaments or cartilage tears.
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