If you have ever heard some say they found out they had a Baker’s cyst, it doesn’t mean they just got back from the bakery with a new pastry for you to try.
It’s more likely that you may have heard someone complain of a large bump on the backside of his/her knee. A Baker’s cyst is also known as a popliteal cyst (named after the location in which these cysts are found). The area behind the knee, at the level of the “bend” is also called the popliteal area, in large part because one of the main arteries (you guessed it, the popliteal artery) passes directly behind the knee as it travels down the leg. The cyst can occur in one or both legs and can get rather large.
One of the most frequent complaints that patients bring to the physician’s office is one of feeling as if there was a golf ball behind the knee. There is frequently no history of any injury and the “bulge” has only become bothersome since it has increased in size.
So, how does a Baker’s/popliteal cyst form, you ask?
A Baker’s cyst typically forms as a result of the collection of synovial fluid – the normal lubricating fluid found in the knee, in the popliteal area in the back of the joint. The fluid does indeed come from inside the knee joint through a small opening in the tissue of the joint capsule. As the fluid escapes into the extra-articular (aka outside-the-joint) space, the opening in the capsule acts as a sort of backflow valve, preventing it from leaching back into the joint. As the condition persists, more fluid escapes into the outer tissues and continues to expand, enlarging the cyst until it becomes noticeable and bothersome.
Baker’s cysts are not the problem, but they are a symptom of a problem – one that is occurring inside the knee joint, such as arthritis, meniscus tears, gout or any other factor that causes irritation to the inside of the knee. In response to inflammation and irritation, the knee instinctively produces additional synovial fluid in its effort to combat whatever the irritant is. The more fluid that is produced, the more internal pressure exists and consequently, the more apt the fluid is to leak out into the popliteal space and form/enlarge a cyst.
So, what do people complain of when they have this cyst?
Most complaints are of an uncomfortable lump in the back of the knee. If large enough, the cyst can also affect and interfere with flexion, or bending of the knee. Some even complain of pain or aching in the back of the knee. Many people also note that during periods of rest, the “bump” may become smaller, only to enlarge again during resumption of activity.
Baker’s cysts are treated in several ways. Conservative treatment typically consists of non-steroidal anti-inflammatory medication to calm the inflammatory response in the knee. If or when these measures no longer work, the cyst can be aspirated, or drained, and injected with a small amount of cortisone. In cases where the size and location of the cyst is such that it compromises nerve or artery function, surgical removal may be necessary.
The important thing to know here is that, while removing the cyst may eliminate the uncomfortable bump, it is still imperative that the cause of the cyst be addressed. Since the cause emanates from inside the knee joint, it may be necessary to obtain an MRI of the knee to assess the status of the internal structures such as the joint cartilage surfaces and menisci (those tough rubbery shock-absorbing cartilages).
Once the cause has been determined (i.e. arthritis, meniscus tear, gout etc.), more definitive work may be required to prevent or minimizes its chances of returning.
So if someone says you look like you swallowed a Titleist Pro-V and it lodged in the back of your knee, you may well have a Baker’s cyst. Get it looked at, inside and out.
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The human skull is 80 percent water... no further comment.
Chisholm’s expertise in nursing, orthopedics and surgery spans more than 30 years. For more information on orthopedic-related topics, visit www.bone-and-joint-pain.com. Submit questions or comments to Ken at
In addition to causing an uncomfortable lump in the back of the knee, a Baker’s cyst, if it becomes large enough, also interferes with bending of the knee. (Photo courtesy of www.emedx.com)