Baker’s Cyst

What are Baker’s Cysts:

Also called popliteal cysts, baker’s cysts occur behind the knee in the popliteal fossa and are fluid filled sacs. They are predominantly asymptomatic and usually discovered during imaging for another unrelated condition.

Symptoms associated with these cysts include knee pain, tightness, and discomfort. Pain worsens with increased activity and decreases range of motion. Inflammation is most visible when the knee is at full extension and least visible at 45 degree flexion.

Lower limb swelling can occur due to the cyst’s impingement of blood vessels and in some cases may present the same as deep vein thrombosis. If the cyst bursts it can cause inflammation/swelling, sharp knee/calf pain and a sensation of water running down the calf. When the cyst busts it can cause nerve entrapment, blood vessel blockage and compartment syndrome.

It is typically diagnosed through physical examination and imaging such as plain radiography, ultrasound and MRI.

Causes:

The knee is a synovial joint where a capsule of synovial fluid cushions between the two bones. Bakers’ cysts can occur when this synovial fluid accumulates and moves between muscle attachments to the knee. This is due to the pressure gradient between the knee joint capsule and fossa moving fluid flow into the fossa.

While more common in adults they can also occur in children. However rather than being caused by a co-morbidity they typically occur when the knee joint capsule herniates.

Commonly occurring in patients aged 35 to 70 years of age or in children 4 to 7 years of age.

Inflammation of the semimembranosus (hamstring) bursa can also cause fluid build up in addition to arthritis, meniscus damage and other degenerative conditions.

Risk factors:

Patients that have a history of trauma to the knee cartilage and meniscus are at greater risk of developing a baker’s cyst. In addition, they commonly occur when patients have degenerative conditions such as arthritis.

Treatment:

If the cyst is asymptomatic and is discovered by accident during imaging or another condition no treatment is typically performed.

Conservative treatment involves behaviour modification such as decreasing aggravating activity and taking anti-inflammatories/pain relief.

In children conservative treatment of the cyst is preferred if the site is not painful and the size of the cyst is less than 3 cm. If the cyst is larger than this and presents with pain surgical excision is considered.

Aspiration (drainage) of the cyst can be performed in which a needle is placed through the posterior leg at the popliteal fossa and into the baker’s cyst. From there a syringe is used – this procedure is performed under ultrasound guidance. Corticosteroid injections into the baker’s cyst aiming to decrease the size of the cyst and relieve pain can also be performed. Risks with these interventions include pain, bleeding, infection, tissue damage and cyst recurrence.

Surgical intervention includes arthroscopy where the degenerative tissue is removed. Complete excision of the cyst can also be performed however this is not recommended in patients that have developed the cyst secondary to degenerative conditions.

Our Osteopaths have found that patients report increased range of motion and improved function after treatment.

References:

Al Khateeb, A. (2024). Bakers Cyst. Baker cyst | Radiology Case | Radiopaedia.org

Fredericksen, K., & Kiel, J. (2021). Bedside ultrasound-guided aspiration and corticosteroid injection of a baker’s cyst in a patient with osteoarthritis and recurrent knee pain. Journal of the American College of Emergency Physicians Open, 2(2), e12424. https://doi.org/10.1002/emp2.12424

Leib, A. D., Roshan, A., Foris, L. A., & Varacallo, M. (2020). Baker’s Cyst. PubMed; StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK430774/

Mansour, M. A., Shehata, M. A., Shalaby, M. M., Arafa, M. A., & Almetaher, H. A. (2021). Baker’s cyst in children: conservative management versus surgical excision according to clinical and imaging criteria. Annals of Pediatric Surgery, 17(1). https://doi.org/10.1186/s43159-021-00071-1

‌Nanduri, A., Stead, T. S., Kupsaw, G. E., DeLeon, J., & Ganti, L. (2021). Baker’s Cyst. Cureus, 13(12). https://doi.org/10.7759/cureus.20403

Patel, C. (29 August 2012). Baker’s Cyst. Baker’s cyst – wikidoc

Van Nest, D. S., Tjoumakaris, F. P., Smith, B. J., Beatty, T. M., & Freedman, K. B. (2020). Popliteal Cysts: A Systematic Review of Nonoperative and Operative Treatment. JBJS Reviews, 8(3), e0139. https://doi.org/10.2106/JBJS.RVW.19.00139