What is a Baker's Cyst?

pain physical therapy Nov 08, 2021
Baker's Cyst
I’ve seen a few Baker’s cysts lately during injury screen events and in some of my post-surgical clients, so I thought it would be a good idea to write up a post on what they are and how to manage them.
A Baker’s cyst, also known as a popliteal cyst, is a collection of fluid behind the knee. It is benign, and often asymptomatic. If it gets severe enough, it can cause pressure on the local nerves and vasculature which will provoke pain and stiffness in the knee. It will usually be difficult to fully flex the knee and you may feel pressure when trying to lock out the knee. The cyst is palpable and sometimes visible.
There is a bursa (fluid-filled sac) behind the knee, which is where the Baker’s cyst occurs. On the medial (inner) side, there is a one-way valve from the knee into that bursa. When there is any type of inflammation in the knee, the swelling builds faster than it can be evacuated, it accrues, and then goes into the bursa. The inflammation that leads to this issue is usually from a degenerative condition, such as cartilage damage, meniscus tearing, osteoarthritis, or rheumatoid arthritis.
These cysts are benign, meaning that they aren’t much of a big deal. Sometimes the cyst can rupture, which will initially cause some pain and swelling in the calf. It is important to note that a DVT (blood clot in the leg) should be ruled out because this can be life threatening. A ruptured cyst can mimic the symptoms of a DVT.
The bursa can be aspirated (drained), but if the underlying issue is not addressed then it will just come back. This is not to say that surgery is necessary, but you need to fix the mechanics that are causing the aggravation. The knee is a hinge joint and its function is dependent on its position and quality of movement. The knee is thought of as a hinge joint that just bends and straightens, but there is actually an element of rotation also. If the knee is rotated internally (knee caved in) or externally (knee bowed out) it can change the relationship of the femur and tibia. If there is some defect, such as a meniscus tear, this rotation can expose it and irritate it. When degenerative tissues get irritated, then swelling starts to accumulate. We need to stabilize the knee by not letting too much rotation or compression occur at the knee.
Where does this rotation come from? More often than not, the ankle. Stand barefoot, and slowly roll your ankle in and out. Watch what it does to your knee. If you are flat footed, it will lead to an internally rotated position of the knee and often cause pain when squatting. To fix this, you have to restore your arch and range of motion in dorsiflexion. That is the most common issue that we see. The hips are also important, because if your hips are not strong enough to keep the knee in the right position, then you can fall into a bad position.
A general principle in rehab is that there are symptoms and dysfunctions. The symptom is the pain/stiffness/swelling that you feel. The dysfunction is what caused the symptom. You sometimes have to look at the adjacent joint(s) to find the dysfunction. Missing range of motion in the ankle changes how you squat, get on/off a seat, and walk. This dysfunction can provoke swelling and pain in the knee, especially if you have an underlying issue. Resolve the range of motion and work on technique, and you just might keep from irritating the knee. If you can keep from irritating your knee, then the cyst can go away naturally and you can start to get stronger with your improved mechanics to prevent this issue from coming back.
If you have a Baker’s cyst, then something is going on. If you’re not sure what that is, get it checked out. I’m not saying you need some sort of procedure or surgery, but if you continue down the path of irritation then you will lose some functional abilities. This is a slippery slope to travel. At Beyond Movement PT, we don’t just treat the symptoms. We will perform a thorough evaluation to determine what is the root cause of your issue. We aim to get you feeling better fast and address the root cause for long-term relief.
Corey Hall, PT, DPT

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