Bakercyste

Bakercyste, commonly known as a Baker's cyst or popliteal cyst, is a fluid-filled swelling at the back of the knee. It is not a tumor and often reflects a change in the knee joint rather than a separate disease. The cyst typically involves distension of the gastrocnemius–semimembranosus bursa or a continued communication with the knee joint that allows synovial fluid to accumulate behind the knee.

Most Baker's cysts arise in the setting of an underlying knee joint disorder, such as osteoarthritis, rheumatoid arthritis, or a meniscal tear. These conditions increase joint fluid production, and a one-way valve mechanism can trap fluid in the posterior knee space, forming the cyst. In children, cysts may occur with effusion from transient knee problems.

Symptoms can include a visible swelling behind the knee, a sense of fullness or tightness, knee pain, and sometimes limited movement. Some cysts are asymptomatic. A ruptured cyst may cause acute calf pain and swelling, which can mimic blood clots or other leg disorders.

Diagnosis is usually based on exam and patient history, with ultrasound commonly used to confirm the cyst and assess its size. MRI may be employed to evaluate underlying joint pathology.

Treatment focuses on the knee problem. Many cysts improve with conservative care: rest, ice, compression, nonsteroidal anti-inflammatory drugs, and physical therapy. Direct treatment of the cyst—such as aspiration or corticosteroid injection—offers temporary relief. Surgery is considered for persistent or recurrent cysts or to repair an associated knee lesion. The cyst may recur if the underlying knee condition persists. The condition is named after the 19th-century British surgeon William Morrant Baker.