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A Bakers cyst is a build up of joint fluid behind the knee. It creates a tight bump behind your knee.

Joint fluid helps the knee move smoothly. A Bakers 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 Bakers cysts
• Cartilage tears, such as a torn meniscus
• Injury or accidents
• Infection in joint

In children, Bakers 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

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Factors that increase your risk of Bakers cyst include:

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

A Bakers cyst may cause:

• Rounded swelling behind the knee
• 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

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 cysts is filled with fluid and not solid.

Images of the knee may be needed to look for the cause. Images may be taken with:

• Ultrasound
• CT scans
• MRI scan
• X-rays (arthrography)

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

Many Bakers cysts resolve on their own without treatment. They may go away within a two-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

There is no known way to prevent a Bakers cyst.