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Knee Pain

Knee Bursitis
- Semimembranosus Bursitis
(Baker's Cyst)

A popliteal cyst, better known as Baker’s cyst, is a fluid-filled swelling that is developed at the back of the knee in the popliteal fossa region.

Ganglia which are benign cystic tumors, originate from synovial tissue. Common areas for cyst can occur at the wrist, hand, foot, and knee.

The cyst can exercise pressure on some anatomical structures, in most cases, the affected anatomical structure is the popliteal vein. Which can develop into thrombophlebitis.


A Bakers cyst is caused by excess fluid in the knee joint. As the joint swells, excess synovial fluid seeps backwards out of the joint and into the popliteal bursa. As the fluid enters the bursa it starts to swell resulting in bursitis.

A number of things can cause the swelling of the knee that leads to a Bakers Cyst:

  • Osteoarthritis: wear and tear of the knee bones and cartilage leads to increased fluid in the knee joint. 50% of arthritis sufferers develop a Bakers cyst at some point. Osteoarthritis is by far the most common cause of Bakers cysts. 

  • Knee Injuries: any injury that results in swelling inside the knee joint increases the risk of developing a popliteal bursitis. The most common injury to cause a Bakers cyst is a cartilage tear. 

  • Inflammatory Arthritis: There are a few types of inflammatory arthritis that increase the risk of developing a Bakers cyst, the most common being gout.