Baker's Cyst - What You Need to Know

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

Photo by Sebastian Kaulitzki (iStockphoto)

What Is a Baker's Cyst?

A Baker's cyst, named after the British surgeon who described it, is a fluid-filled sac that is caused by excess knee-joint fluid. Excess fluid (produced by the lining of the joint) pushes through the back part of the joint capsule (fibrous tissue that surrounds or envelopes 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."

What Causes a Baker's Cyst to Form?

A Baker's cyst can develop after the joint capsule becomes damaged or weakened. Swelling in the knee joint -- whether it be from arthritis (especially osteoarthritis), injury, a cartilage tear or overuse of the joint -- causes damage to the joint capsule.

What Symptoms Are Associated with 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 the knee is extended, it can 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.

How Is a Baker's Cyst Diagnosed and Treated?

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.

In most cases, a Baker's cyst can be treated nonsurgically. 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 for people who find the cyst painful or particularly bothersome. Even after it is surgically removed, there is a likelihood that the Baker's cyst will recur.


Baker's cysts in knees with chronic osteoarthritic pain: a clinical, ultrasonographic, radiographic and scintigraphic evaluation. Rheumatology Int. June 27, 2008. Chatzopoulos D, et al.

A Patient's Guide to Popliteal Cysts. eOrthopod. July 23, 2002.

Continue Reading