What Is Baker Cyst?

Overview

If you have ever noticed a bulge in the back of your knee or experienced discomfort, you may be dealing with a Baker's cyst. A Baker's cyst, often referred to as a popliteal cyst, is a common knee condition marked by the emergence of a swelling filled with fluid at the back of the knee.¹ It frequently develops from underlying knee joint issues, including osteoarthritis or a torn meniscus, which cause an excessive amount of fluid to be produced.² When this fluid exits the knee joint in one direction, a sac that develops into a Baker's cyst is created. A Baker's cyst frequently results in stiffness, irritation, and occasionally pain, especially if it ruptures. Full knee extension or flexion movements can make the pain worse. 

If you discover a lump or growth behind your knee, you should contact a doctor immediately. A medical professional can assess the situation and make suitable therapy recommendations. Even though a Baker's cyst can cause swelling and discomfort, fixing the underlying issue usually relieves the condition. Sometimes, the cyst may even disappear on its own without any medical intervention.

This article provides a clear understanding of Baker's cyst, including its causes, associated risk factors, symptoms, diagnostics, and available treatment options.

Causes of Baker’s cyst

An inflammatory response brought on by multiple knee conditions causes excessive production of synovial fluid, which is essential in lubricating the knee and lowering friction inside the moving joint. A Baker's cyst may then develop as a result of this fluid gathering at the back of the knee.

The most common causes of Baker's cysts are knee arthritis and injuries. The emergence of Baker's cysts is frequently accompanied by the following types of arthritis:

• Osteoarthritis: Typically linked to age-related joint wear and tear
• Rheumatoid arthritis: A less frequent condition when the immune system mistakenly targets the joints
• Gout:  Develops when uric acid waste products build up in the bloodstream 

While gout typically affects the big toes, Baker's cysts can also form as a result of it.

Aside from arthritis, a number of knee injuries can also play a role in the formation of Baker's cysts. These injuries include:

• Sport-related injuries: From direct blows to the joint
• Repetitive strain injuries: Overuse issues after repetitive movements and excess pressure
• Meniscus tears: A tear of C-shaped cartilage in the knee joint, disrupting normal knee function and contributing to excessive synovial fluid production
• Ligament injuries: ACL, PCL, MCL, and LCL are the ligaments that surround the knee joint. When they are damaged, it causes instability and inflammation in the knee joint

The causes listed above are not exhaustive, and any condition that results in damage or inflammation of the knee joint can potentially cause the development of a Baker's cyst.

Signs and symptoms of baker cyst

Baker's cysts may not always exhibit symptoms and are frequently found by chance during a physical examination or when getting a magnetic resonance imaging (MRI) scan for another reason. When symptoms do arise, they may present themselves in the following ways:

• Pain at the back of the knee
• Stiffness in the knee joint
• Obvious protrusion or swelling behind the knee, especially when the leg is straight

People frequently find that standing for extended periods of time, or bending the knees excessively makes the pain worse. In addition, activity might also worsen the symptoms and swelling. Sometimes, Baker's cysts can burst, releasing fluid into the nearby tissues. Additional symptoms, such as calf swelling and redness or bruising below the knee, could develop if this happens.³

There may also be symptoms that are predominantly related to an underlying joint condition, such as instability brought on by internal dislocation or joint discomfort from inflammatory arthritis or osteoarthritis.

Management and treatment for baker cyst

Most cysts, especially asymptomatic ones, resolve on their own; thus, therapy may not be essential. However, if the baker’s cyst persists or produces symptoms, the following nonsurgical remedies are usually used to treat it in the beginning:

• Rest: Symptoms may improve by reducing high-impact activities that put a strain on the knee
• Ice: Applying a cold compress for 10-20 minutes every hour to reduce swelling
• Compression: Compression bandage reduces blood flow to the injured knee and reduces swelling
• Elevation
• Medications: NSAIDs (Nonsteroidal Anti-Inflammatory Drugs), like ibuprofen or naproxen, may be prescribed to reduce pain and swelling. If inflammation fails to improve, corticosteroids can be administered directly into the knee joint
• Aspiration: By using ultrasound imaging as a guide, a needle can be used to drain the cyst's extra fluid.⁴

The initial approach to the ruptured cyst is similar. 

Rarely if nonsurgical options are unsuccessful or the cyst keeps reappearing, surgical procedure is taken into consideration:⁵

• Arthroscopy: A minimally invasive technique that addresses underlying problems like meniscus tears by inserting a tiny camera and surgical tools into the knee joint⁶
• Excision: The entire cyst may be removed by an open surgical operation in cases of large cysts or when they create nerve or vascular concerns

Your surgeon will explain the type of surgery you'll require and what to expect during the healing process.

Diagnosis

Diagnosis of a Baker's cyst in patients with a popliteal mass can typically be made solely on the basis of medical history and physical examination. Your doctor will ask about your symptoms and whether you've ever had knee issues before. Your injured knee will be thoroughly examined, with your unaffected knee used as a reference.

Imaging studies are occasionally conducted in certain patients when there is uncertainty in diagnosis or suspicion of another condition, but they are typically not necessary.⁷

• X-rays - utilised to take pictures of dense structures, such as bones. Although a cyst cannot be seen on an X-ray, one may be requested to evaluate symptoms of arthritis in the joint and the narrowing of the joint space.
• Ultrasound - using sound waves to create images of internal body structure. It provides a clearer picture of the lump behind the knee and helps identify whether it is solid or liquid-filled.
• MRI - provides clear images of soft tissues in the body. It is used to gather additional information about the cyst and investigate the presence of a meniscus tear or other underlying conditions.

Complications

Popliteal cysts can expand, tear, or burst, compressing adjacent structures resembling vein inflammation (thrombophlebitis). Additional symptoms, such as acute pain, swelling, and a sense of fluid movement, can be brought on by a burst Baker's cyst in the knee and lower leg. Although they can happen, complications like impaired blood flow, nerve entrapment, cyst infection, and compartment syndromes are not frequently reported. Acute pain typically subsides after a few days, but because of the size of the cyst, chronic swelling may cause knee flexibility to be limited.

FAQs

How can I prevent baker cyst?

Avoiding knee injuries is crucial for lowering the risk of Baker's cysts appearing or returning. Warming up and cooling down, wearing the proper footwear, and avoiding putting too much stress on the knees can all help. It is advised to stop any physical activity right away, apply ice packs, and consult a doctor if you have a knee injury.

How common is baker cyst?

Popliteal cysts are commonly discovered incidentally during imaging tests performed for other purposes. They are more likely to occur in adults aged 35 to 70.⁸ Depending on the imaging technique utilised, the frequency of popliteal cysts in individuals with knee problems might range from 5 to 40%. These cysts tend to appear more frequently as people age, and there is no discernible difference in frequency between men and women.

Who are at risks of baker cyst?

A history of knee trauma, which is present in around one-third of patients, and concomitant joint disorders found in two-thirds of patients are risk factors for the formation of popliteal cysts in adults. Osteoarthritis, rheumatoid arthritis, and meniscal tears are common knee conditions linked to popliteal cysts.

When should I see a doctor?

It is advised to see a doctor if you have any of the aforementioned symptoms or a persistent bulge behind your knee that is bothering you. It's crucial to understand that not all knee swelling is a Baker's cyst. A doctor can look at your knee, listen to your complaints, and advise you on the best course of action.

Summary

A Baker's cyst is a swelling filled with fluid at the back of the knee. It is frequently linked with underlying knee joint disorders like arthritis or traumatic injuries. The cyst may result in swelling, stiffness, and pain. If a lump is seen behind the knee, medical assessment is advised, especially in people with arthritis or recent knee injury. While rest, ice, compression, elevation, NSAIDs, and cyst aspiration are among the possible treatments for cysts, most of them resolve independently. If non-surgical treatments fail,  arthroscopy or excision may be performed. Diagnostic tests, including X-rays, ultrasounds, and MRIs, may occasionally be utilised for additional analysis in addition to the standard medical history and physical examination. Complications can occur, but they are uncommon. Through adequate warm-up, footwear, and avoiding excessive knee stress, knee injuries can be prevented. It's critical to contact a doctor if you have symptoms or a persistent knee bulge.