Baker's Cyst

Baker’s cyst is a condition, in which there is an accumulation of synovial fluid (joint fluid) behind the knee. It is a lump filled with synovial fluid. Baker’s cyst is named after William Morrant Baker, the British surgeon, who first described this condition. It causes swelling and a feeling of tightness in the popliteal area of the knee. Therefore, Baker’s cyst is also named as a popliteal cyst. Baker’s cyst is formed when a bursa (a small sac of fluid behind the knee) overfills with synovial fluid and expands. It generally results from a knee injury or certain kinds of arthritis or a cartilage tear. Approximately one in five people with certain knee problems may develop Baker’s cyst.

Causes of Baker’s Cyst

Certain knee problems including knee injuries such as ligamentous injuries and meniscus injuries, inflammation of knee joint due to various types of arthritis and cartilage tear can lead to Baker’s cyst. In these conditions, excess amount of synovial fluid is produced, which is accumulated behind the knees. Osteoarthritis is the most common type of arthritis associated with Baker’s cyst. Baker’s cyst may also result from rheumatoid arthritis and other knee problems. A local knee infection can also cause fluid retention around the knee joint.

Symptoms of Baker’s Cyst

Generally, Baker’s cyst causes no pain and remains unnoticed. A large cyst may cause some stiffness or discomfort. It appears like a water-filled balloon. A person may experience knee pain, a feeling of tightness behind the knee and restricted mobility of the joint. There is swelling behind the knee and sometimes in the leg. Sometimes, this cyst ruptures, leaking the fluid down the inner leg. It can cause swelling, pain and bruising behind the knee and in the calf.

Diagnosis of Baker’s Cyst

Baker’s cyst is diagnosed with the help of physical examination, imaging tests such as X-ray, MRI scan and ultrasound. Transillumination or passing a light through the cyst is a helpful method to detect the fluid-filled cyst. MRI scan is helpful to detect the cyst as well as to demonstrate any meniscal injury. Arthrogram is another effective method for diagnosing the Baker’s cyst. In this method, a contrast dye is injected into the knee joint.

Treatment for Baker’s Cyst

In many cases, Baker’s cyst heals on its own and no treatment is required. If the cyst is too large and quite painful, then you need to seek an appropriate medical treatment. It is treated with medications, fluid drainage and physical therapy. Medications such as acetaminophen or nonsteroidal anti-inflammatory drugs (NSAIDs) can be used to alleviate pain. Cortisone injections into the knee help to reduce inflammation as well as relieve pain. The excess fluid accumulated in the knee joint is drained using a needle. This procedure is known as needle aspiration and is often performed under ultrasound guidance. Various physiotherapy treatments such as compression wrap, icing and crutches may also help reduce swelling and pain. Certain strengthening exercises and gentle range-of-motion exercises (under the guidance of a professional) can help manage the symptoms and maintain knee function. If a cartilage tear is the cause of Baker’s cyst, then your doctor could recommend surgery to remove or repair the torn cartilage.