Baker’s cyst is a synovial fluid-filled sac that forms in the back of your knee, typically located on the medial side (inside) of the knee, between the semimembranosus and the medial head of the gastrocnemius. Baker’s cyst is more commonly found in adults aged 35-70 and often secondary to inflammatory joint diseases such as rheumatoid arthritis, osteoarthritis, meniscal tears, overuse or trauma to the knee. In children, baker’s cyst most often occurs between age 4 to 7.
Baker’s cyst can be diagnosed through a physical examination. By having the individual stand and extend the knee in full, the cyst is observable and palpable. And when the knee is flexed to 45 degrees, the mass usually softens or disappears (i.e. Foucher’s sign).
Often treatment is not necessary when the patient is asymptomatic with the baker’s cyst. Continued observation and reassurance by a health care professional is often sufficient. However, the presence of the cyst may come with a sensation of tightness, discomfort or pain behind the knee, as well as the inability to fully flex or extend the knee. As the baker’s cyst grows bigger, it may even compress the surrounding vessels, resulting in swelling in the calf area.
Symptomatic baker’s cyst can be managed by physiotherapy. Physiotherapists can help decrease pain and swelling of the affected area and treat the underlying joint diseases of the knee. Physiotherapists can also ensure there is good knee range of motion, prescribe stretching and strengthening exercises.
Some typical non-operative treatments of baker’s cyst include rest or activity modification, anti-inflammatory medications, cortisone injection to the knee, ultrasound-guided aspiration of the cyst by an interventional radiologist.
Lastly, it is very important to rule out other possible disorders that present with similar symptoms as Baker’s cyst, these include deep vein thrombosis, solid masses (i.e. sarcomas or lymphoma), or popliteal artery aneurysms. Consult your primary care providers if you have any questions!
Reference: Leib, A. D., Roshan, A., Foris, L. A., & Varacallo, M. (2017). Baker's Cyst.