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 Baker's cyst.
What causes a Baker's cyst?
Baker's cysts in children often involve the bursa, a small sac of fluid behind the knee. The bursa may join with the sac that cushions the knee bones (synovial sac) to form a cyst.
Arthritis is the most common cause in adults, but a Baker's cyst also can be caused by a knee injury. The swelling from these problems causes fluid to build up in your knee. The cyst forms when the fluid pushes out in the back of the knee.
What are the symptoms?
Often a Baker's cyst causes no pain. When symptoms occur, they may include:
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 as an 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.
Other Works Consulted
- American Academy of Orthopaedic Surgeons and American Academy of Pediatrics (2005). Popliteal cyst section of Knee and lower leg. In LY Griffin, ed., Essentials of Musculoskeletal Care, 3rd ed., pp. 557–559. 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.
|Primary Medical Reviewer||William H. Blahd, Jr., MD, FACEP - Emergency Medicine|
|Specialist Medical Reviewer||Kenneth J. Koval, MD - Orthopedic Surgery, Orthopedic Trauma|
|Last Revised||August 3, 2010|
Last Revised: August 3, 2010
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