Baker’s cyst, also known as a popliteal cyst or a synovial cyst, is a fluid-filled lump or growth that develops at the back of the knees. It occurs due to the build-up of synovial fluid in the knee joint thus causing inflammation and swelling of the tissues behind the knee, resulting in pain and stiffness which worsens with activity or when the knee is bent or straightened.

However, if inflammation or swelling of the knee should occur, the knee responds by producing an excess of synovial fluid, which flows to the popliteal bursa behind the knee, causing it to swell and grow, resulting in a Baker’s cyst. 

Inflammation and swelling of the knee can occur due to:

• Injury: injuries to the knee such as meniscus injuries, ACL injury/tear, can cause the build-up of synovial fluid in the knee joint, resulting in a Baker’s cyst.
• Medical conditions: arthritis such as osteoarthritis and rheumatoid arthritis causes inflammation of joints, thus resulting in a Baker’s cyst. Gout is also a type of arthritis that can eventually result in Baker’s cyst.

However, some individuals may experience the following symptoms:

• Fluid-filled lump or growth behind the knee
• Pain or discomfort
• Limited or reduced range of motion
• Stiffness in the knee joint
• Swelling and inflammation of the knee joint
• Reduced ability to bend the affected knee
• Inability to fully flex the affected leg 
• Numbness if the Baker’s cyst has compressed a nerve

These individuals may also experience a reduced range of motion and stiffness in the affected knee joint. 

These factors are:

• Knee joint injury or conditions: individuals with knee joint injury such as meniscus tears or ACL injuries/tears, or knee conditions such as osteoarthritis or rheumatoid arthritis, are at an increased risk of developing Baker’s cyst.
• Age: your risk of developing Baker’s cyst increases with age.
• Sports/hobbies: high contact sports or hobbies that put you at a higher risk of knee injuries will by default increase your risk of developing Baker’s cyst.

• Physical examination and medical history: inform your orthopaedist about any prior knee injury or conditions that may have led to the development of the Baker’s cyst. Physically the area of concern will be examined and several motion tests such as bending and straightening the injured knee will be conducted. 

• Imaging tests: x-rays will be conducted to identify if arthritis is present, which may identify the cause of your Baker’s cyst. Magnetic resonance imaging (MRI) can also be used to identify other causes of your Baker’s cyst such as ACL tears/injuries and meniscus injuries. Ultrasounds can also be conducted to identify if the lump is fluid-filled.

Treatment for Baker’s cyst include:

• Medications: non-steroidal anti-inflammatory drugs (NSAIDs) and painkillers are commonly prescribed as the first course of treatment to reduce inflammation and manage pain.
• Injections: corticosteroid injections may be used to manage pain and relieve symptoms associated with a Baker’s cyst. 
• Rest: rest from physical activity is usually prescribed until symptoms reduce. The use of a crutch may also be recommended to reduce putting any strain or pressure on the affected knee.
• Aspiration: the fluid from the cyst can be drained or removed if it does not resolve on its own.
• Physiotherapy: physiotherapy which involves the use of gentle and therapeutic exercises, may be prescribed to preserve and improve knee mobility and function. 
• Surgery: though rarely needed, arthroscopic knee surgery can be conducted if you are experiencing intense or severe knee pain, or if you are unable to move your knee.