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Health Matters: The mysterious baker’s cyst

Conway McLean, DPM, Journal columnist

Presented today for your amusement, a common scenario about another painful medical condition. Some hard-working person, performing a physically demanding job, develops some new and uncomfortable sensations from their leg. Pain can interfere with both work and play. A common area of concern for many of us is the knee, a joint essential for all manner of daily activities. Knee pain can occur for a multitude of reasons, one often reported is the dreaded Baker’s Cyst. What is it and why are they painful? All your pressing questions about them are about to be answered.

A more accurate term for the condition is popliteal cyst, the first word describing that region, the back of the knee. A cyst is a fluid-filled mass, wherever it may be. These fluid-filled lumps in this popliteal area are common, and often cause no symptoms, so estimates of their frequency are hard to come by. The more interesting question is why these lumps appear. Apparently, the explanation boils down to one of fluid dynamics.

No, this is not a discussion of the inner workings of a university physics lab. When certain knee problems are present, the production of joint fluid, that all-important lubricant, increases. This extra liquid can cause swelling of the joint, but can also flow into a small space behind the knee. It enlarges when filled with the extra fluids and, voila, a Baker’s cyst has formed.

Should you be wondering, these lumps are not confined to the baking industry. Instead, these are named after Dr. William Morrant Baker who published a description of it in the mid-1800’s. Back in those times, a documented treatment for a Baker’s cyst was amputation, which seems a rather dramatic solution. But this condition had been recognized even earlier by several others. Clearly, this is not an unusual anomaly. It turns out it is a combination of two common situations that lead to the formation of a popliteal cyst.

In the case of the knee, many of us have an anatomical variation allowing passage of any excess joint fluid into a compartment that exists where a calf muscle attaches behind the knee joint. After extensive research, it was found some of us have a connection between the knee joint and this compartment. When present, this passageway has a duct allowing passage out of the joint but not back. Yet a critical component in the formation of a popliteal (aka Baker’s) cyst is some inflammatory condition of the inside of the knee joint. When there is some condition of the knee’s interior causing greater fluid production, it leaks into the cyst.

Returning to our “typical” patient, they are often in their 40’s or 50’s when the mass is first noticed. It would seem many people with a Baker’s Cyst are asymptomatic, having no pain or problems. Often the mass is detected only accidentally, perhaps during a physical exam, or when certain studies of the knee are done. A very common early symptom, when there ARE symptoms, most frequently consists of swelling. Others may note stiffness or tightness of the knee joint. Sometimes, soreness will extend into the upper calf, especially when they straighten or bend the knee repeatedly.

Again, in mild cases, a Baker’s cyst causes no noticeable signs. Likewise, it can also disappear mysteriously, without any treatment. If the cyst grows too large, symptoms are more likely to be experienced and so need medical attention. Often, those who are experiencing symptoms from this problem will notice greater pain when they are more active. Some sufferers will first feel an uncomfortable, swollen lump behind their leg. But controversy exists surrounding the numbers, how many people have one of these. No study has been published stating how many of these cause problems and what percentage of us have an asymptomatic one.

Despite the opinion of the uniformed, conservative measures exist for a painful Baker’s cyst, from the use of oral anti-inflammatories (the ubiquitous ibuprofen) to icing and compression. Surgical removal of the cyst without treatment of the problem inside the joint has been reported, but isn’t recommended due to the high rate of recurrence. Arthroscopic debridement and closure of the opening leading to the cyst has been reported but remains experimental. Ideally, treating the primary problem, the joint malady, be it osteoarthritis or a damaged meniscus, is highly recommended. This often leads to resolution of the cyst, but not always. (And no, amputation is no longer recommended.)

Despite the great variability in its presentation, the degree of symptomatology, the amount of pain produced, a Baker’s cyst can be a source of some difficulty. It need not be ignored, but should be considered a signal of some “deeper” problem. The internal joint abnormality must be addressed. Modern medicine is capable of great things but requires a willing patient. Take an interest in your health, watch for changes and new lumps and bumps. For many medical problems, early detection leads to better health.

Editor’s note: Dr. Conway McLean is a physician practicing foot and ankle medicine in the Upper Peninsula. Dr. McLean’s practice, Superior Foot and Ankle Centers, has offices in Marquette and Escanaba, and now the Keweenaw following the recent addition of an office in L’Anse. McLean has lectured internationally, and written dozens of articles on wound care, surgery, and diabetic foot medicine. He is board certified in surgery, wound care, and lower extremity biomechanics.

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