A Baker cyst is a buildup of joint fluid behind the knee. It creates a tight bump behind the knee.
Joint fluid helps the knee move smoothly. A Baker cyst happens when excess fluid is pushed out to the back of the knee.
Sometimes the cause is not known. In adults, it may be due to underlying problems with the knee joint. In children, it may be due to problems with the small fluid-filled sac (bursa) between the bone and soft tissue of the knee.
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Things that may raise the risk of this problem in adults are:
- Past knee injuries or cartilage tears
- Osteoarthritis—wear and tear of cartilage between bones
- Inflammatory diseases, such as rheumatoid arthritis and gout
- Previous knee surgery
Things that may raise the risk of this problem in children are:
Problems may be:
- Rounded swelling behind the knee that may get bigger with activity
- Aching or tenderness after exercise and bending the knee
- Pain or pressure in the back of the knee
- Pain that may travel to the calf
The doctor will ask about your symptoms and health history. A physical exam will be done. It will focus on the knee.
Images of the knee may be taken. This can be done with:
The problem may go away on its own without treatment. In others, the underlying cause may need to be treated.
A cyst that is painful or impacting daily life may need to be treated. The goal of treatment is to manage symptoms and promote healing. Options are:
- Medicines to ease pain and swelling, such as:
- Over the counter pain relievers
- Corticosteroid injection
- Physical therapy to improve strength, flexibility, and range of motion
- Draining excess knee fluid with a needle
People who are not helped by these methods may need surgery. It may be done to remove the cyst or repair a damaged knee joint.
There are no current guidelines to prevent this health problem.
Ortho Info— American Academy of Orthopaedic Surgeons
Sports Med—American Orthopaedic Society for Sports Medicine
Canadian Orthopaedic Association
Canadian Orthopaedic Foundation
Frush TJ, Noyes FR. Baker's Cyst: Diagnostic and Surgical Considerations. Sports Health. 2015 Jul;7(4):359-365.
Popliteal cyst. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/popliteal-cyst. Accessed January 29, 2021.
Last reviewed December 2020 by EBSCO Medical Review Board Teresa Briedwell, PT, DPT, OCS, CSCS Last Updated: 1/29/2021