Baker cyst appears as a fluid-filled nodule or sac located behind the knee.
Its presence is, in some cases, asymptomatic while, in others, it is associated with swelling, pain, or sensation of joint stiffness. In reality, however, Baker’s cyst is nothing more than the manifestation of another associated and preexisting pathology.
So let’s see what it is, trying to understand its causes and analyzing possible solutions.
What is Baker cyst
Baker cyst or popliteal cyst is a benign tumefaction that forms behind the knee (in a region referred to as the popliteal), causing more or less palpable swelling and making knee flexion and extension difficult.
Its size can vary greatly. While in some patients it is so large that it is visible to the naked eye, in other cases it is identified only after specific tests such as ultrasound or MRI.
The presence of the cyst may be associated with knee pain, usually localized in the inner and/or posterior region. However, it rarely occurs in a healthy knee: in fact, a degenerative pathology of the meniscus (most often medial or internal), usually associated with initial cartilage wear, is almost always responsible for its formation.
Not surprisingly, this issue mainly arises after the age of 40 and, especially, in the 50-70 range, when it is more common for there to be other knee joint disorders (such asosteoarthritis) that can promote synovial fluid leakage and, consequently, cyst formation.
To treat the pain associated with Baker’s cyst, therefore, it is not enough to perform an aspiration of it; instead, it will be necessary to act on the cause responsible for the accumulation of synovial fluid.
Origin of Baker cyst
The mechanism underlying Baker cyst formation is a degenerative pathology of the knee. In fact, initial cartilage wear is frequently associated with wear of the articular margin of the meniscus.
These initial conditions set the stage for the three fundamental events that contribute to Baker cyst formation:
- An increase in synovial fluid production by the knee; this is a defense mechanism the joint puts in place to “lubricate” a “gear” that is beginning to wear out.
- The “book-like” opening of the two leaflets of the injured meniscus; the increased intrarticular pressure allows synovial fluid to find a way out between the upper and lower layers of the meniscus.
- Cyst development; synovial fluid gradually forms a cyst, finding easily dilated tissue in the posterior space of the knee.
The popliteal area most frequently affected by this synovial fluid accumulation is between the semimembranosus and gastrocnemius muscles.
Complications
Although these are extremely rare occurrences, the presence of Baker cyst can sometimes lead to complications:
- The rupture of the cyst, felt by the patient as a sharp pain posterior to the knee, pain that, however, tends to disappear within a few days.
- Deep vein thrombosis, due to the venous compression that such a formation can exert on the vessels posterior to the knee
Diagnosis
The clinical finding of tumefaction is strongly indicative that we are dealing with a Baker cyst.
To confirm this diagnosis, anultrasound can be done, a quick and easy examination that is performed with short waiting times by contacting our National Health System.
But, since baker’s cyst is often associated with cartilage wear and tear, one should lean toward a more thorough “snapshot” of the knee: MRI. This examination, in fact, allows for a very precise evaluation of the joint structures and, in particular, the cartilage and menisci.
Baker cyst treatment
As Baker cyst is a secondary manifestation of pre-existing cartilage and meniscal degenerative pathology, aspiration or removal of the cyst will resolve only the sensation of “compression” but not the associated joint pain.
Should such compression cause moderate or severe pain, however,aspiration of the cyst with possible injection of NSAIDs or cortisone will result in marked improvement of this issue. Subsequent ice placement, rest, and the use of oral anti-inflammatories may then inhibit its recurrence.
Beyond these palliatives, it will still be necessary to search for the primary cause responsible for the abnormal accumulation of synovial fluid by studying the knee joint. Articular cartilage consumption, particularly of the medial compartment, will need to be quantified to evaluate possible arthroscopic meniscal treatment, correction of the knee axis, or infiltrative therapies to protect the cartilage.
In cases where Baker cyst is associated with advanced osteoarthritis with ineffectiveness of bloodless treatments, knee arthroplasty will be considered.
