Discusses Baker's cyst (also called popliteal cyst), a pocket of fluid that forms a lump behind the knee. Covers causes such as swelling from arthritis and knee injury. Discusses symptoms. Covers treatment, including things to do at home and surgery.
What is a Baker's cyst?
A Baker's cyst is a pocket of fluid that forms a lump behind the knee.
It is also called a popliteal cyst. See a picture of a
What causes a Baker's cyst?
A Baker's cyst is caused when excess joint fluid is pushed into one of the small sacs of tissue behind the knee. When this sac fills with fluid and bulges out, it is called a cyst. The excess fluid is usually caused by conditions such as rheumatoid arthritis or osteoarthritis that irritate the knee. It may also be caused by an injury.
What are the symptoms?
Baker's cyst causes no pain. When symptoms occur, they may include:
Tightness or stiffness behind the
Swelling behind the knee that may get worse when you
Slight pain behind the knee and into the upper calf. You are
most likely to feel this when you bend your knee or straighten it all the
Sometimes the pocket of fluid behind the knee can tear open
and drain into the tissues of the lower leg. This can cause swelling and
redness in that part of the leg.
How is a Baker's cyst diagnosed?
Your doctor will examine your knee and ask
you questions about your past health and when the pain and swelling started.
Your doctor may order tests, such
MRI, to see a picture of the inside of your knee.
How is it treated?
A Baker's cyst may go away on its own.
If arthritis or another problem is causing the Baker's cyst, your doctor
may treat that problem. This usually makes the pain and swelling of a Baker's
cyst go away.
If a cyst does not go away, or if it is causing a
lot of pain, your doctor may drain the fluid with a needle. You also may be
given a shot of
steroid medicine to reduce swelling. You may need to
use a cane or crutch and wrap your knee in an elastic bandage. In rare cases, a
Baker's cyst is removed by surgery.
There are things you can do
at home to help you feel better.
Use a cane, crutch, walker, or another device if you need help to
get around. These can help rest your knee.
If you wear an elastic
bandage around your knee, make sure it is snug but not so tight that your leg
is numb, tingles, or swells below the bandage. Loosen the bandage if it is too
Follow your doctor's instructions about how much weight you
can put on your knee.
Stay at a healthy weight. Being overweight
puts extra strain on your knee.
Other Works Consulted
American Academy of Orthopaedic Surgeons and American Academy of Pediatrics (2010). Popliteal cyst. In JF Sarwark, ed., Essentials of Musculoskeletal Care, 4th ed., pp. 716–718. Rosemont, IL: American Academy of Orthopaedic Surgeons.
Hanada E, et al. (2008). Baker's cyst. In WR Frontera et al., eds., Essentials of Physical Medicine and Rehabilitation: Musculoskeletal Disorders, Pain, and Rehabilitation, 2nd ed., pp. 315–317. Philadelphia: Saunders Elsevier.
William H. Blahd, Jr., MD, FACEP - Emergency Medicine
Kenneth J. Koval, MD - Orthopedic Surgery, Orthopedic Trauma
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