What are Baker's Cysts? Causes & Symptoms Explained!
Last reviewed on 25 October 2025 by Danniel Jacques (B.Med.Sci UNSW)
What is a Baker’s Cyst?
A baker cyst is a painful condition which can be characterised by swelling in the back of the knee.
This swelling occurs due to inflammation in the synovial joint which encapsulates the knee resulting in the out-pouching of fluid into a little balloon type sac from the synovial lining.
When this condition develops, synovial fluid (which is normally contained in a tough capsule that encases the knee joint) collects in the Baker’s cyst and bulges behind the knee.
This is also called a “popliteal cyst” as it directly affects the popliteal region of the knee (that shallow depression located behind the knee joints).
If left untreated it is possible for it to rupture. A ruptured baker’s cyst may then cause the collected synovial fluid to transfer and travel down the calf muscles of the legs. This can then trigger rapid swelling and discomfort of the leg which may then cause further complications.
What Causes a Baker’s Cyst?
Baker’s cysts are quite common and can be caused by nearly any joint-related inflammation. Some of the most common causes may include;
- A micro tear in the knee’s meniscal cartilage
- Repetitive stress injury.
- Wear & tear in the knee (which is more common in older adults)
- Injury to the anterior cruciate ligament of the knee (ACL injury)
- Sports-related injury that affects the knee
- The type of work that a person does may also make them more susceptible. This include jobs that involve being on your knees, such as a gardener or carpenter. Also such jobs that require long shifts without sitting or unusual weight loading through the knees such as nursing.
A Baker’s cyst is also know as a >> popliteal cyst
What are the Symptoms of a Baker’s Cyst?
Symptoms may include visible swelling or protrusion on the back of the knee (which can be either with our without pain), constant and prolonged knee pain, and tightness at the back of the knee or simply a feeling of tenderness at the back of the knee.
If left untreated a Baker’s cyst may actually rupture. A ruptured or burst Baker’s cyst can cause a lot of pain and discomfort and can present very similarly as a blood clot as there will also often be calf related pain.
How to diagnose a Baker’s cyst?
It is always best to visit a qualified medical professional if you suspect that you have either a Baker’s cyst or feel that your Baker’s cyst may have ruptured or burst.
Your doctor will likely require you to have an ultrasound which will be able to confirm a diagnosis of Baker’s cyst and also importantly rule out or alert the doctor of any existence of a blood clot.
If there is an infection suspected then a blood test and maybe an aspiration of the synovial fluid may be required for testing and culturing. In some cases an x-ray and or MRI may also be required to rule out any co-exist conditions that may have contributed to the condition.
