Baker's Cysts: What You Need to Know

When severe, a Baker's cyst can be mistaken for a blood clot

Photo by Sebastian Kaulitzki (iStockphoto)

Baker's cysts are fluid-filled sacs caused by excess knee-joint fluid.

This common condition occurs when excess fluid produced by the lining of the knee joint pushes through the back part of the joint capsule (the fibrous tissue that surrounds the joint), forms a cyst and protrudes into the back area of the knee, known as the popliteal fossa. A Baker's cyst may also be referred to as a "popliteal cyst."

If you have osteoarthritis or rheumatoid arthritis, you may be familiar with this painful condition. Fortunately, there are treatment remedies available for Baker's cysts, depending on the cause. 

Causes of Baker's Cysts

Baker's cysts have nothing to do with actual bakers; they're named for William Morrant Baker, the British surgeon who first discovered them. Anyone of any profession can develop a Baker's cyst, especially after a knee injury or due to a chronic knee condition. 

Simply put, a Baker's cyst can develop after the joint capsule becomes damaged or weakened. It's caused by swelling in the knee from arthritis or an injury such as a cartilage tear or a meniscus tear.

It's important to verify whether your condition is, in fact, a Baker's cyst since there's the possibility of serious complications such as deep vein thrombosis, which can lead to the formation of a blood clot.

Symptoms of a Baker's Cyst

A Baker's cyst can be soft to the touch and slightly tender.

You may have no symptoms other than a visible bulge behind the knee or a tight feeling that something is behind the knee. When you extend your knee, this can make a Baker's cyst become tighter or more painful.

A Baker's cyst can actually swell or shrink. It also can burst underneath the skin, and the consequence of a burst Baker's cyst are symptoms very much like those associated with blood clots: redness and pain in the calf.

The fluid from the ruptured cyst is absorbed by the body. When this happens, the Baker's cyst temporarily disappears, but it usually comes back.

Diagnosing and Treating a Baker's Cyst

A physical examination is usually all that is needed to diagnose a Baker's cyst. MRIs or ultrasounds can be used to confirm that the cyst is fluid-filled, as opposed to solid.

Depending on the underlying condition that causes it, in most cases, a Baker's cyst can be treated without surgery. Nonsurgical treatment would include:

  • draining the fluid from the cyst using a needle and syringe
  • cortisone injection to reduce inflammation
  • rest
  • elevating the leg
  • icing to reduce inflammation
  • physical therapy regimen to control swelling
  • treating the underlying condition

Surgical removal of a Baker's cyst is an option if you find the cyst painful or particularly bothersome. Even after it is surgically removed, it's possible that a Baker's cyst will recur. In most cases, however, treatment of the injury that caused the Baker's cyst will alleviate symptoms and reduce the likelihood that it will recur. 

Sources:

Zhou, X., et al. "Surgical treatment of popliteal cyst: a systematic review and meta-analysis" Journal of Orthopedic Surgery and Research  Feb. 2016, 11:22 

Frush, T., Noyes F. "Baker's Cyst: Diagnostic and Surgical Considerations" Sport Medicine July 2015  (4):359-65. 

Herman A., Marzo, J. "Popliteal Cysts: A Current Review" Orthopedics, August 2014 7(8):e678-84

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