Health and Fitness

What Causes a Meniscal Cyst?

Did you know that meniscal cysts got initially reported in 1883? Until lately, clinicians thought that cysts in the medial meniscus were less common than the lateral meniscus. Therefore, recent studies revealed that using advanced imaging techniques and arthroscopic picturing approximate that 59-66% of cysts develop medially, while 34-41% develop laterally. These facts encourage us to explore the details. So, this article will highly what causes meniscal cyst?

What is Meniscal Cyst? 

The cyst develops in the meniscus cartilage when your joint fluid collects on the joint pad positioned on the knee. It might have little or no symptoms. Sometimes, you may feel pain, inflammation, or mechanical problems with your knee. These cysts usually occur in young makes and are commonly linked with a particular type of meniscus tear regarded as horizontal cleavage tear. Generally, the tear develops as a result of either direct hit or over-rotation of the knee.

The most prevalent ways of diagnosis are Magnetic Resonance Imaging (MRI) or ultrasound. And your doctor will use pioneering and safe methods to drain the accumulated fluid in the cyst. Though, it is likely to refill unless you get a meniscus tear treated.

What are the Symptoms?

As mentioned earlier, this condition might show little or no symptoms. However, the most common signs and symptoms include: 

  • Pain behind knee when you raise from the chair
  • Sensitivity right on the joint line of your knee 
  • The appearance of a bulge or swelling at the place where the cyst is growing. 
  • An outgrowth that becomes more visible when you stretch the knee. Although, the lump might be painless. 
  • Size variation of the cyst, though it may also remain the same size.
  • Knee joint swelling or locking 

What are the Causes?

So, according to experts, the meniscal cyst is a degeneration of the meniscus itself that may be due to ageing, the development of arthritis, or direct injuries. Direct injuries include an impact on the front or side of your knee. Over-rotation of the knee or uneven force on the knee (when running or walking on bumpy pathways) may also trigger it. So, these incidents may cause meniscus cartilage, leading to the escape of synovial fluid from the joint. Hence, the accumulation of the fluid leads to the development of a cyst. 

So, this cyst is not an actual cyst, instead an outgrowth of dislocated synovial or joint fluid. Therefore, it is your body’s natural healing mechanism as a response to the meniscus tear injury. As your body’s function include the constant formation of new synovial fluid and absorption of extra fluid. However, when fluid seeps away from the joint, it accumulates and develops into a lump. 

So, your cartilage tear can perform as a single-way valve, where the fluid can outflow the joint space into the lump. Unfortunately, it does not escape from the other passage. So, due to this, the cyst continues to amass fluid. 

What are the Risk Factors? 

Meniscal outgrowth risk factors may include: 

  • Former knee injury or meniscal damage 
  • Involvement in sports (especially contact sports) may require repeated knee joint twisting. Some examples of contact sports may consist of football, soccer, rugby, or tennis. 
  • Growing age or osteoarthritis can trigger degeneration of the meniscus 
  • Related tendon injuries, like torn anterior cruciate ligament (ACL)

What is the Diagnosis? 

Typically, experts diagnose the meniscus tear or cyst through physical examination or MRI test. However, currently, there are no practical medical examination tests to detect cysts.

Your physician may inquire from you some particular questions linked to knee pain, strange sounds, and recent knee damages to decide if you are suffering from a meniscal tear. However, a cyst gets palpated, and your doctor will then evaluate your knee’s range of motion to ascertain no ripped cartilage pieces are stuck in your joint.  

Standard tests for evaluating meniscal tear and other knee damage include the McMurray test, the Apley test, the Steinmann I trial, the Payr’s test, Childress’ sign, and the Ege’s test. However, if your doctor wants a further investigation of your condition, they may order magnetic resonance imaging (MRI) to examine the outgrowth and the tear. 

Imaging Tests

Radiographic Features 

Usually, you will find the cyst in your medial meniscus along the posterior side of the posterior horn. And, the cyst in your side meniscus is along the frontal or anterolateral side of the anterior horn.

Plain radiograph

Plain radiography is a means of obtaining a picture of internal structures by passing X-rays through them, and recording the shadows cast by these structures. It may reveal soft tissue inflammation at possible locations.


A high-res musculoskeletal ultrasound can be extremely sensitive and display an anechoic or a hypoechoic lesion in being with cystic nature of the lesion. It may also highlight the related meniscal tear.


It is the detailed investigation of choice for all-inclusive imaging of the knee. So, the majority of cysts are non-palpable, and you may experience knee pain. So, MRI is required to detect the meniscal tear and cyst.


As per the report of Dr Pisani, he defined pathognomonic signs of 30+ patients of the meniscal lump. A hemisphere-shaped cyst vanished into the knee joint on acute flexion and returned on the knee extension. It reached a max dimension of 25-30 degrees short of full extension. Therefore, experts examined the Pisani sign in 10 patients suffering from lateral knee puffiness most prominent at 30-45 degrees of knee curve and arthroscopically set adjacent para-meniscal cyst. Though the joint line pudginess connected well with the existence of meniscal tear, however, it did not link well with the presence of meniscal cyst in the new approaching cohort study.

Comparison: Meniscal Vs Baker’s Cyst

Did you know that baker’s cyst is quite similar to meniscal lumps? However, a baker’s cyst is in the back of the knee joint. Besides, a popliteal cyst may form due to several knee joint issues (that may cause fluid build-up or knee inflammation), like a meniscus tear. However, if you have arthritis, tendon injuries, and other problems may also cause swelling. 

What is the Treatment? 

If you feel pain due to a meniscus cyst, you can treat it through ice therapy. Anti-inflammatory medicines can also help improve the condition. Apart from this, your doctor may safely drain out your cyst in their clinic. However, unless your doctor does not treat the underlying cause of the tear, the problem is likely to reoccur.


Sometimes, experts cannot treat this problem without surgery. Although, if your doctor deems appropriate, they might use a minimally-invasive arthroscopic surgery. After the doctor treats the tear, the cyst is likely to decompress and not regrow. However, removing the cyst might not be necessary so that the doctors may treat the underlying cause only.


Some people might get scared of cysts. You need to understand that a cyst on your meniscus is just a pouch of the displaced joint fluid. It is not an abnormal outgrowth, so it is not a tumor. However, it is just an average accumulation of fluid.

So, if you don’t feel any pain, you may continue your normal routine activities. However, if you feel any symptoms like pain, swelling, or knee locking, you should immediately visit a knee specialist and follow appropriate measures.

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