Baker's Cyst

A Popliteal Cyst Caused By Fluid Accumulation

knee posterior
A Baker's cyst causes fluid accumulation in the back of the knee joint. Great Art Productions / Getty Images

A Baker's cyst, also called a popliteal cyst, is a collection of fluid in the back of the knee joint. A Baker's cyst is usually a sign of a problem causing fluid accumulation inside the knee joint.

It's Not a Tumor

A Baker's cyst is not a growth, in fact, it's not even a real cyst.  To be called a true cyst, the fluid collection must have a specific type of cell lining.  A false cyst (or pseudocyst), is caused by a fluid accumulation that simply collects in a space it then cannot get out of.

  In the case of a Baker's cyst, the fluid comes from the knee joint, and then pools in the back of the knee.

Therefore, a Baker's cyst is not a tumor, it is not a cancer, and it will not spread to other parts of your body.  A Baker's cyst to a doctor is really just a symptom or a sign to look for a problem inside of the knee joint that could be causing excess fluid to accumulate.

Cause of the Cyst

Most often in adults the Baker's cyst is found in conditions where there is chronic swelling or fluid accumulation in the knee joint. These conditions include knee arthritis, meniscus tears, and ligament injuries.   A Baker's cyst can also be caused from synovial fluid accumulation in inflammatory conditions such as rheumatoid arthritis, Lyme arthritis, and gout.

The typical symptoms of a Baker's cyst include:

  • Swelling felt in the back of the knee
  • Discomfort and tightness in the back of the knee
  • Difficulty fully bending the knee backwards

    A Baker's cyst has nothing to do with the baking profession.  The reason many people call this a Baker's cyst is that the condition was first described in the 1800s by a doctor named Dr. William Baker.  Many doctors today wish it was never called a "cyst" because this is not an accurate description of the condition.

      What people call a Baker's cyst can be more accurately called "posterior knee swelling."

    Treatment Options

    Treatment of a Baker's cyst should be focused on treating the underlying knee joint problem that is causing the fluid accumulation. These treatments may include anti-inflammatory medications, rest, physical therapy, and cortisone injections. In some patients, a knee surgery may be recommended, but again, the surgery is focused on treating the source of the fluid accumulation, not the Baker's cyst itself.

    There are rare circumstances where a surgeon may try to directly address the cyst.  In these cases, the options are to remove the accumulated fluid through a needle, or perform surgery to directly remove the cyst.  As stated, these are very rare circumstances, as if the cause of the fluid accumulation is not addressed, the problem is very likely to return.  In addition, a Baker's cyst is often intertwined with important blood vessels and nerves in the back of the knee that, if damaged, can cause more problems than the cyst would cause.

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