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.
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.
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Baker's cyst
Hello,
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Baker's cyst
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Baker's cyst
Thank you.
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Baker's cyst
Hi, just a quick note that I feel I needed to write about the OSMO Patches. In September I tripped over while running and fell on my knee which left me with a fractured bone at the back of my knee which in turn ruptured my cruciate ligament. Although back on track now after various braces, crutches and hydrotherapy plus physiotherapy, it seemed I had gained a cyst at the back of my knee. This tight swelling really hindered my ability to improve and I looked to the internet for answers-where I found your advert
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Baker's Cyst
I’ve had bakers cyst under my knee cap for 5 years and I’ve been in constant agony and haven’t been able to bend my knee for 5 years.
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Bakers Cyst on the knee
I hurt my knee quite severely when out bushwalking in the Mt Mitchell National Park. I hadn’t been doing much strenuous walking and on the way down I got a nasty pain in my knee.
My doctor told me I had a Bakers Cyst on the knee. I found your website and the OSMO Patch sounded like a good idea and I ordered it. It arrived within seven days of placing the order and it relieved the pain overnight. I find if I use the patches for three nights (until it’s dry) I have no pain for several weeks.
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Baker's cyst
Good morning
We have been using your patches for a few days now and we find them helpful.
They are draining fluid from the cyst and that is a good sign.
Real accounts by real people. Hear what they have to say!
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Thank you for responding.
I think I will save my last two patches in case I need them. Right now, I have such great improvement, I am no longer wearing the knee brace and I can walk up and down stairs with alternating feet.
Have not done that for a while!
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I’ve had a Baker’s cyst behind my right knee, caused by an injury, for 4 years.
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Hello Danniel,
Thank you for your prompt reply.
I started using the patches about 10 days ago, and the amount of improvement is unbelievable. The lump was rock hard, and I could not bend the knee, nor straighten the leg. Even though there is still some swelling, the knee feels almost normal. I have run out of the patches, so will restart as soon as I receive the new batch…hopefully it will all go away.
Thank you for your help, and good luck..
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Hi,
I got the patches yesterday evening. I have had five knee operations on my right knee and have arthritis. I also have a baker’s cyst on the back of my knee and off to the front.
I tried it last night and I was surprised at the results and it actually took away some of the swelling. I work out every other day and I think these will help.