Are you experiencing a lump or bump on the outside of your knee that becomes more visible when you straighten your leg following a knee injury? You may have a parameniscal cyst, which often develops after a meniscus tear.
Although parameniscal cysts usually aren't serious, they can cause knee pain, swelling, and decreased mobility. However, with a proper diagnosis and appropriate treatment, you can return to your normal activities.
What is a parameniscal cyst?
A parameniscal cyst, also called a meniscal cyst, is a small sac of synovial fluid (joint fluid that lubricates your knee) that forms around your meniscus. Your knee meniscus is the C-shaped cartilage that acts as a shock absorber between your thigh and shin bones, cushioning your knee joint when you walk, run, or jump.
The cyst develops when you experience a meniscal tear due to a sudden twist, pivot, or impact injury. The tear creates a pathway for the joint fluid to escape and collect around the surrounding area. These cysts can form on either the inside or outside of your knee, but external parameniscal cysts are more common.
Parameniscal cyst symptoms
Parameniscal cysts don't always cause symptoms. However, you may notice or feel a firm bump or lump, most commonly on the outside of your knee joint. Other symptoms that may appear include:
Pain that worsens when you stand on the affected leg
Knee swelling and stiffness
Tenderness along the affected knee joint
Clicking or popping sounds during movement
Limited range of motion
A bump that becomes more apparent when you straighten your knee
Risk factors
The primary cause of a parameniscal cyst is a meniscus tear, particularly horizontal cleavage tears. However, there are several risk factors that can increase your likelihood of developing this condition. These include:
Previous knee injury
Meniscal degeneration (osteoarthritis) due to ageing
Genetic factors that increase the risk of joint issues
Direct impact to the front or side of the knee joint
Ligament injuries, such as ACL tear
Participating in sports involving sudden twisting or pivoting movements (e.g., soccer or basketball)
Applying disproportionate force to the knees, such as when running on an uneven surface
As we age, the meniscus will wear down and weaken. Thus, leading to it getting thinner and compromises its ability to absorb impact, meaning it can be injured by relatively low-impact movements such as squatting or getting up from a chair.
If you have any of the aforementioned risk factors or suspect that you might have a meniscus cyst based on your symptoms, schedule an appointment with Thomson Medical. Our specialist can help diagnose your condition and create a personalised treatment plan.
How are parameniscal cysts diagnosed?
To diagnose a meniscal cyst, your doctor will ask you about the symptoms you're experiencing, such as knee pain, and when you first noticed the lump. They will also look at your medical history to discover whether you have had any previous knee injury.
After the initial examination, your doctor will conduct a physical exam or pressure test on your knee joint, which includes the following procedures:
The McMurray test:
For this test, you will lie on your back while your doctor flexes your knee fully and then extends it with rotational movements.
The Apley test:
During this test, your healthcare provider will bend your knee to 90 degrees, applying downward pressure while rotating your lower leg.
The Payr's test:
During the test, your doctor will bend your knee as far as possible, then gently rotate and press your lower leg to see if it causes any pain or discomfort.
The Ege's test:
The Ege's test involves bending your knee to 90 degrees, rotating your foot outwards, and applying pressure while straightening your knee.
Any clicking, popping or pain that occurs during the test may indicate a parameniscal cyst injury.
To confirm the diagnosis, your healthcare provider may perform imaging tests, such as Magnetic Resonance Imaging (MRI) or ultrasound scans. These tests allow your healthcare provider to assess the size and location of the cyst, evaluate the condition of your meniscus and identify any additional knee problems that may require treatment.
Treatment options
Treatment for a meniscus cyst depends on the severity of your conditions. Mild cases might be managed with conservative treatments at home, while more severe or persistent symptoms may require surgical intervention. Here are the available treatment options:
Non-surgical treatment
For mild symptoms or as initial treatment, your healthcare provider might recommend:
Avoiding any activities that can worsen your symptoms.
Applying ice to the affected knee joint.
Nonsteroidal anti-inflammatory drugs (NSAIDs) to help reduce pain and inflammation.
Physical therapy to improve knee strength, flexibility, and range of motion while reducing stress on the meniscus.
Cyst aspiration or drainage involves your doctor using a thin needle to drain the joint fluid. However, if an underlying medial tear remains untreated, this approach will only offer temporary relief, as the fluid will often return.
Surgical treatment
If conservative treatment fails to improve your condition, your doctor might recommend a surgical procedure. Usually, this technique comprises a minimally invasive process called arthroscopic surgery, where a small camera is inserted through small cuts around your knee. This procedure usually includes:
Arthroscopic decompression: A procedure where your doctor repairs the damaged meniscus cartilage to stop the joint fluid from leaking out and developing a cyst, enabling the joint to decompress naturally.
Direct cyst excision: A procedure in which your doctor removes the cyst tissue, typically used for large or complex cysts.
To find out which treatment is right for you, schedule an appointment with Thomson Medical. Our specialists can help assess your condition and determine which treatment options are suitable for you.
How to prevent parameniscal cysts in the knee
Currently, there is no effective way to prevent meniscal cysts. However, there are some steps you can take to reduce your risk of developing this condition, such as:
Strengthening your leg muscles to support the knee joint
Address meniscal injuries early to prevent cyst formation
Use proper techniques during sports and exercise
Use protective equipment to avoid direct impact to the knee joint during sports
FAQ
Do parameniscal cysts go away on their own?
Parameniscal cysts rarely disappear on their own without treatment. While they may occasionally shrink or become less noticeable, they usually persist because an underlying meniscal tear continues to allow joint fluid to leak out.
Although some cysts may remain asymptomatic for extended periods, the fluid-filled sac will typically remain present until the root cause is addressed.
What is the treatment for a cyst in the knee joint?
Treatment depends on your symptoms and how much the cyst affects your daily activities. Conservative approaches include rest, ice therapy, cyst drainage, anti-inflammatory medications, and physiotherapy to strengthen your knee.
However, if symptoms persist or significantly impact your quality of life, your doctor may recommend arthroscopic surgery to repair the meniscal tear and address the cyst.
How painful is a parameniscal cyst?
Pain levels can vary considerably from person to person. While some people experience no discomfort and only notice a visible lump, others may experience significant pain, which worsens when they stand on or use the affected leg during physical activity.
Is draining a parameniscal cyst possible?
Yes, your doctor can drain the cyst using a thin needle guided by ultrasound imaging. This procedure is called aspiration and often involves injecting corticosteroids to reduce inflammation. However, this type of therapy is usually only a temporary solution, as the cyst will often refill with fluid unless the underlying meniscal tear is also treated.
How big are parameniscal cysts?
Parameniscal cysts can vary significantly in size, ranging from a few millimetres to over 4 centimetres in diameter. On average, they measure 1.25 centimetres.
Larger cysts are more likely to cause noticeable symptoms, such as pain, swelling and visible lumps, and they may require surgical intervention. Smaller cysts may remain undetected and be discovered incidentally during imaging for other knee problems.
Can you have a parameniscal cyst without a tear?
Yes, it is possible to have a parameniscal cyst without a meniscal tear, but this is quite rare. The vast majority of these cysts are caused by an underlying tear in the knee cartilage.
When cysts occur without tears, they may be caused by problems with ligament fibres, or they may be a different type of cyst, called a ganglion cyst.
This information is intended as general guidance only and should not be considered as medical advice. For personalised health screening recommendations based on your children's medical conditions, schedule an appointment with Thomson Medical.
For more information, contact us:
Thomson Specialists (Thomson Medical Centre) — Orthopaedic
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