Got a lump on the back of your knee? Somebody mention Baker’s Cyst or popliteal cyst? Although it may be news to you, these are more common than many people suspect. While not normally an isolated finding, there are two bursae (bursas) in the back of the knee joint which can fill with fluid. Even though it feels like a mass, and when we think mass we think cancer and these have nothing to do with cancer. Most commonly these are a secondary process in reaction to something going on in the knee joint itself. They are neither life nor limb threatening but can be quite bothersome. They are not the result of an infection. People who have them will report that some days they’re large, some small, and while intermittently painful, the patient can actually be symptom free for much of the time.
The mass or fullness is actually fluid that has filled the cyst, much the consistency of the normal fluid found in a human joint. Often times they will accompany arthritis in the older patient and, although less frequently, a torn knee cartilage (meniscus) in the young.
If one is diagnosed with this problem, a number of options will be discussed and one of them is simply to do nothing. Many patients, once they discover that it’s not cancer, will choose this option. Others prefer an aspiration of the cyst and injection of a steroid preparation. If still symptomatic to the point where, if a potentially treatable issue is uncovered, the next step might include plain x-rays and follow up MRI. These might be stepping stones to arthroscopy. In the patient with enough arthritis, and an accompanying Baker’s Cyst,to warrant a knee replacement simply replacing the joint (not so simple for either patient or surgeon) will lead to resolution of the cyst.
Lastly, very infrequently, no other causative agent can be located and the patient will request excision of the cyst. This is pretty rare in my experience.
So, if your doc tells you that you have a Baker’s Cyst, there’s no rush to do anything, analyze your options and after weighing the risks/benefits choose what’s best for you. Patience is always helpful.