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8054 Yonge St. Thornhill. Just south of the intersection of Yonge and HWY 7/407

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WILDERMAN MEDICAL CLINIC

Anatomy of knee

The knee joint is made up of three bones: the femur (thigh bone), tibia (shin bone), and patella (kneecap). These bones are held together by ligaments, which provide stability to the joint.

The knee joint also contains two types of cartilage: articular cartilage, which covers the ends of the bones and allows them to glide smoothly against each other, and meniscal cartilage, which acts as a cushion between the femur and tibia.

The knee joint is filled with a clear synovial fluid that acts as a lubricant to help reduce friction within the joint. There are several bursae, which are small fluid-filled sacs in the knee joint, which help reduce friction between the muscles and other surrounding structures.

The synovial fluid circulates through these bursae. A valve-like system regulates the flow of the synovial fluid between the popliteal bursa (which is located behind the knee joint) and the knee joint.

What is a Baker’s cyst?

An overproduction of synovial fluid in the knee can cause an accumulation of fluid in the popliteal bursa, causing a Baker’s cyst, also known as a popliteal cyst. The term “Baker’s cyst” comes from Dr. William Morrant Baker, an English surgeon who first described the condition in the 19th century.

This condition is usually the result of underlying knee joint pathologies, such as osteoarthritis, rheumatoid arthritis, or meniscal tears.

When a Baker’s cyst forms, it can cause swelling and pain behind the knee, sometimes even radiating into the calf. Depending on the size and location of the cyst, it can push against surrounding structures, including blood vessels and nerves, which can cause additional symptoms.

How common are Baker’s cysts?

Baker’s cysts are relatively common and can occur in both adults and children.

The incidence rate of Baker’s cysts is not well documented in the medical literature; however, some studies suggest that the prevalence of Baker’s cysts in people with knee problems ranges from 4% to 19%.

One study by Baker and colleagues (2007) reported a prevalence of 19% in a population of patients with knee osteoarthritis.

Another study by Magee and colleagues (2006) reported a prevalence of 4% in a population of patients with knee pain. Additionally, the incidence of Baker’s cysts may increase with age and in people with underlying joint conditions such as osteoarthritis or rheumatoid arthritis.

What are the causes of Baker’s cysts?

The following are some of the most common causes of Baker’s cysts:

  • Knee joint arthritis: Osteoarthritis and rheumatoid arthritis are two common types of arthritis that can cause inflammation in the knee joint, leading to the production of excess synovial fluid and the development of a Baker’s cyst.
  • Meniscal tears: A meniscal tear occurs when the cartilage in the knee joint is torn or damaged. This can cause inflammation and an increase in synovial fluid production, leading to the formation of a Baker’s cyst.
  • Other knee joint injuries: Any injury that causes inflammation in the knee joint, such as a ligament sprain or strain can lead to the formation of a Baker’s cyst.
  • Gout: Gout is a type of arthritis that occurs when uric acid crystals build up in the joints, causing inflammation and pain. Gout can also cause a Baker’s cyst to form.
  • Infection: In rare cases, an infection in the knee joint can cause the formation of a Baker’s cyst.

What are the symptoms of a Baker’s cyst?

The symptoms of a Baker's cyst can vary depending on the size of the cyst and the underlying cause of the knee joint condition. Some of the most common symptoms associated with a Baker’s cyst include:

  • Swelling: A Baker’s cyst typically causes a noticeable swelling behind the knee. The swelling may be soft and fluctuant and can range in size from a small lump to a large mass.
  • Pain: Baker’s cysts can cause pain behind the knee, especially when the knee is fully extended or when the person is active. The pain may be sharp or dull, and it may be accompanied by a feeling of tightness or stiffness in the knee.
  • Limited range of motion: A Baker’s cyst can limit the range of motion in the knee joint, making it difficult to fully extend or flex the knee.
    Clicking or popping: Some people with a Baker’s cyst may experience a clicking or popping sensation when they move their knee joint.
  • Sensation of fullness: The swelling from a Baker’s cyst can cause a feeling of fullness or pressure behind the knee as if something is pushing against the back of the knee.
  • Complications: In some cases, a large Baker’s cyst can put pressure on surrounding structures, such as blood vessels and nerves, leading to complications such as leg swelling, numbness, and tingling.

How is a Baker’s cyst diagnosed?

The following are the methods commonly used for diagnosing Baker’s cyst:

  • Physical examination: A doctor or healthcare provider can usually diagnose a Baker’s cyst through a physical examination. During the exam, the doctor will look for swelling behind the knee and may palpate the area to feel for a fluid-filled mass.
  • Diagnostic imaging tests: Imaging tests, such as ultrasound, MRI, and X-ray, can help confirm the diagnosis of a Baker’s cyst and rule out other knee joint conditions that may have similar symptoms. An ultrasound can provide a detailed view of the fluid-filled mass, while an MRI can show the extent of the cyst and any associated knee joint problems. X-rays may be used to check for any bony abnormalities or to rule out other causes of knee pain.
  • Joint aspiration: In some cases, a doctor may perform a joint aspiration to confirm the presence of a Baker’s cyst. During this procedure, a needle is inserted into the cyst to extract a sample of the fluid. The fluid is then sent to a laboratory for analysis. Typically, a combination of physical examination and imaging tests is used to diagnose Baker’s cyst.

How is a Baker’s cyst treated?

The treatment options for a Baker’s cyst may vary depending on the underlying cause of the knee joint condition and the severity of the symptoms. Some treatment options may include:

  • Rest and ice: Mild cases of Baker’s cyst may improve with rest and ice therapy. Resting the knee and applying ice packs to the affected area can help reduce swelling and pain.
  • Medications: Over-the-counter pain medications, such as acetaminophen or nonsteroidal anti-inflammatory drugs (NSAIDs), may help relieve pain and reduce inflammation.
  • Injection therapy: In some cases, a doctor may recommend injecting a corticosteroid medication into the knee joint to help reduce inflammation and alleviate symptoms of the Baker’s cyst.
  • Physical therapy: Physical therapy may be recommended to improve flexibility, strength, and range of motion in the knee joint. Stretching and strengthening exercises can help relieve symptoms and prevent the recurrence of the cyst.
  • Surgery: In rare cases, a large or symptomatic Baker’s cyst may require surgical removal. The procedure may involve draining the cyst, removing the cyst wall, or repairing any underlying knee joint problems that may be contributing to the cyst. Following surgery, the recovery process will include rest, possible knee immobilization with a brace, and physical therapy to help strengthen and improve the range of motion of the knee joint.
What Causes Baker’s Cyst? - Illustration of the problem

It is important to consult with a doctor or healthcare provider to determine the best treatment approach for your individual case of Baker’s cyst.

What do we do at WMC?

At the Wilderman Medical Clinic, we offer a variety of interventional and non-interventional pain management options, including:

Interventional pain management for Baker’s cyst:

  • Ultrasound-guided aspiration of the Baker’s cyst
  • Ultrasound-guided injection with cortisone for Baker’s cyst
  • Ultrasound-guided PRP injection for Baker’s cyst
  • Ultrasound-guided dextrose prolotherapy for Baker’s cyst

Non-interventional pain management for Baker’s cyst:

  • Psychotherapy
  • Kinesiology education sessions

Reference

Parker, James N., & Parker, Philip M. (2004). Baker’s Cysts: A Medical Dictionary, Bibliography, And Annotated Research Guide To Internet References. ICON Health Publications.

Koman, A. H., & Teng, M. W. (2016). Baker’s Cyst: Diagnosis and Management. Journal of the American Academy of Orthopaedic Surgeons, 24(4), 200-207. doi: 10.5435/JAAOS-D-15-00202

Herring, C. D., & Skaggs, R. J. (2011). Baker’s cysts in children: diagnostic considerations and treatment options. Journal of the American Academy of Orthopaedic Surgeons, 19(11), 686-691. doi:10.5435/00124635-201111000-00003

Mayo Clinic. (n.d.). Baker’s cyst. Retrieved April 11, 2023, from https://www.mayoclinic.org/diseases-conditions/bakers-cyst/symptoms-causes/syc-20369950

American Academy of Orthopaedic Surgeons. (2021, October). Baker’s cyst (popliteal cyst). OrthoInfo. Retrieved April 11, 2023, from  https://orthoinfo.aaos.org/en/diseases–conditions/bakers-cyst-popliteal-cyst/

NHS. (2022, February 14). Baker’s cyst. Retrieved April 11, 2023, from https://www.nhs.uk/conditions/bakers-cyst/

Baker, K., et al. Prevalence of Popliteal Cysts Detected by Magnetic Resonance Imaging in Osteoarthritis Patients. Annals of the Rheumatic Diseases, vol. 66, no. 7, 2007, pp. 981-983.

Magee, T., et al. Popliteal Cysts: A Current Review. Orthopedics, vol. 29, no. 7, 2006, pp. 576-583.