Joint fluid helps the knee move smoothly. A Baker cyst develops when there is too much of this fluid. The extra joint fluid is pushed out to the back of the knee. Extra fluid may be caused by:

Arthritis — osteoarthritis is the most common type associated with Baker cysts
Cartilage tears, such as a torn meniscus
Injury or accidents
Infection in joint

In children, Baker cyst may be related to a problem with the bursa. The bursa is a small fluid filled sac between the bone and soft tissue.

Bursa

Risk Factors

Factors that may increase your chance of a Baker cyst include:

Osteoarthritis
Rheumatoid arthritis
Infectious arthritis
Gout
Past knee injuries or cartilage tears
History of corticosteroid injection around the knee
Previous knee surgery
Knee synovitis

Symptoms

A Baker cyst may cause:

Rounded swelling behind the knee that may get bigger with activity
Pain or pressure in the back of the knee joint—may travel to the calf muscle
Aching or tenderness after exercise and bending the knee

Diagnosis

Your doctor will ask about your symptoms and medical history. A physical exam will be done. The doctor will look for a soft mass in the back of the knee. The range of motion in both knees will be tested and compared. The doctor may also shine a special light through the cyst. This will show that the cyst is filled with fluid and not solid.

Images of the knee occasionally needed to look for the cause and extent of the cyst . Images may be taken with:

Blood tests may be taken if there may be an infection.

Treatment

Many Baker cysts resolve on their own without treatment. They usually go away within a 2-year period.

The underlying cause may need treatment. This may include knee repairs or medication to treat medical conditions.

Treatment for the cyst itself may be needed if the cyst is painful or interferes with daily activities. Treatment options include:

Medications to relieve pain and inflammation such as nonsteroidal anti-inflammatory drugs (NSAIDs)
Physical therapy to help strengthen muscles around the knee
Steroid injection
Draining excess knee fluid
Surgery—to remove large cysts or repair related knee injuries

Prevention

There are no current guidelines to prevent Baker cysts.

RESOURCES:

Ortho Info— American Academy of Orthopaedic Surgeons
http://www.orthoinfo.org

Sports Med—American Orthopaedic Society for Sports Medicine
http://www.sportsmed.org/patient

CANADIAN RESOURCES:

Canadian Orthopaedic Association
http://www.coa-aco.org/patient/public-information.html

Canadian Orthopaedic Foundation
http://www.canorth.org/

References:

Calmbach WL, Hutchens M. Evaluation of patients presenting with knee pain: Part II. Differential diagnosis. Am Fam Physician. 2003;68(5):917-922.

Fritschy D, Fasel J, et al. The popliteal cyst. Knee Surg Sports Traumatol Arthrosc. 2006;14:623-628.

Popliteal cyst. EBSCO DynaMed Plus website. Available at: http://www.dynamed.com/topics/dmp~AN~T116564/Popliteal-cyst . Updated May 17, 2017. Accessed November 10, 2017.

Torreggiani WC, Al-Ismael K, et al. The imaging spectrum of Baker’s (popliteal) cysts. Clin Radiol . 2002; 57:681-691.

Ward EE, Jacobson JA, et al. Sonographic detection of baker’s cysts: comparison with MR imaging. AJR Am J Roentgenol. 2001: 176:373-380.

Last reviewed November 2018 by EBSCO Medical Review Board Warren A. Bodine, DO, CAQSM
Last Updated: 12/20/2014

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