What is a Baker’s cyst?
A Baker’s Cyst is an abnormal collection of synovial fluid in the fatty layers of the popliteal fossa or the soft tissues in the posterior aspect of the knee. A Baker’s Cyst can also be called a popliteal cyst. A Baker’s cyst can be mistaken for a semimenbranous bursa, which is a fluid filled sac that acts as a cushion between tendons, bones, and skin.
The semimenbranous bursa can enlarge with repetitive flexing of the knee. Both are located on the medial side of the popliteal fossa. Both can enlarge with the overproduction of synovial fluid, but the baker’s cyst is separate from anatomical structures. How does it occur? A cyst can occur when the lining of the knee joint produces too much fluid. This can occur in rheumatoid arthritis, osteoarthritis, repetitive irritation of the joint, or injury.
What are the symptoms?
You may experience tightness or swelling behind the knee or pain down the back of the leg. You may also fill a lump behind the knee. Occasionally cysts can rupture causing a sharp pain behind the knee that can radiate down the back of the leg. How is it diagnosed? Your doctor will examine your knee for a palpable, cystic mass in the medial aspect of the popliteal fossa.
Also a specific history can determine the cause of the synovial fluid over production. Large cysts can impair range of motion of the knee joint. It is important for your doctor to examine for signs of vascular insufficiency including a popliteal aneurysm and a deep venous thrombosis. Your doctor may request special diagnostic testing including a magnetic resonance image (MRI), arthrogram, or ultrasound.
How is it treated?
The initial discomfort of a Baker’s cyst may be treated with compression, wearing an elastic bandage. Your doctor may prescribe anti-inflammatory medications. Your doctor may perform an aspiration or possibly surgery to remove the cyst. In general, small cysts should be observed. The treatment for large cysts that interfere with full function of the knee is local aspiration and corticosteriod injection. Surgical removal is considered if all caused of excessive fluid production have been treated optimally, and if the cyst is interfering with normal function of the knee.
Occasionally, the cyst can go away on it’s own. If the cyst does not cause bothersome symptoms, it may not be treated. How can a Baker’s cyst be prevented? There is really no way to prevent a Baker’s cyst from forming. Even with surgical removal, a Baker’s cyst can reappear. The best option is treating the recurrent effusion occurring in the knee joint.
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