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What is a baker's cyst behind your knee

Baker's cyst - NHS

A Baker's cyst, also called a popliteal cyst, is a fluid-filled swelling that develops at the back of the knee.

A Baker's cyst on a leg



It's caused when the tissue behind the knee joint becomes swollen and inflamed. The swelling and inflammation can cause:

  • pain in the knee and calf
  • a build-up of fluid around the knee
  • occasional locking or clicking in the knee joint

However, sometimes a Baker's cyst may not cause any symptoms other than the fluid-filled swelling at the back of the knee.

A Baker's cyst can sometimes burst (rupture), resulting in fluid leaking down into your calf. This can cause sharp pain, swelling and redness in your calf, but redness can be harder to see on brown and black skin.

What causes a Baker's cyst?

Knee damage caused by a sports injury or a blow to the knee can lead to a Baker's cyst developing.

A Baker's cyst can also sometimes occur if you have a health condition such as:

  • osteoarthritis – usually caused by age-related "wear and tear" of joints; it particularly affects the knees, hips, hands and big toe
  • inflammatory arthritis – including rheumatoid arthritis, which is a less common type of arthritis and is caused by the immune system attacking the joints
  • gout – a type of arthritis that usually affects the big toe and is caused by a build-up of the waste product uric acid in the blood

Baker's cysts usually develop in people aged 30 to 70, although they can affect people of any age, including children.

When to see your GP

See your GP if you have a lump behind your knee that's causing problems and does not clear up on its own. They'll usually be able to diagnose a Baker's cyst by examining the back of your knee and asking about your symptoms.

Your GP will ask you whether you have any associated health conditions, such as arthritis.

Tests may be recommended to rule out other more serious conditions, such as a tumour, an aneurysm (bulge in a section of a blood vessel) or DVT (deep vein thrombosis) (a blood clot in one of the deep veins of the body). You may need an ultrasound scan or a MRI scan.

Treating a Baker's cyst

Treatment will not usually be necessary if you have a Baker's cyst that is not causing any symptoms.

Painkillers such as paracetamol and ibuprofen can be used to reduce the swelling and relieve any pain. A knee support or an ice pack may also help. A bag of frozen peas wrapped in a tea towel works well as an ice pack.

If you have an underlying condition that's causing your cyst, it's important that the condition is properly managed. The cyst may disappear when the condition causing it has been treated.

In some cases, it may be possible to drain the cyst. Surgery may also be needed to repair any significant damage around the knee joint.

Read more about treating a Baker's cyst.

Page last reviewed: 04 October 2021
Next review due: 04 October 2024

Baker's Cyst (Popliteal Cyst) - OrthoInfo

Baker’s cysts, also known as popliteal cysts, are one of the most common disorders in the knee. These fluid-filled cysts form a lump at the back of the knee that often causes stiffness and discomfort. The condition is named after the 19th century surgeon who first described it, Dr. William Morrant Baker.

Baker’s cysts typically result from a problem inside the knee joint, such as osteoarthritis or a meniscus tear. These conditions cause the joint to produce excess fluid, which can lead to the formation of a cyst.

Most Baker’s cysts will improve with nonsurgical treatment that includes changes in activity and anti-inflammatory medications. Some cysts may even go away on their own, with no treatment at all.

A Baker’s cyst (arrow) can cause a sense of fullness behind your knee, especially when you straighten your leg.

The knee is the largest and strongest joint in the body. It is made up of the lower end of the femur (thighbone), upper end of the tibia (shinbone), and the patella (kneecap). A smooth, slippery tissue called articular cartilage covers and protects the ends of the bones where they meet to form a joint.

The knee joint is filled with a clear fluid (synovial fluid) that acts as a lubricant to help reduce friction within the joint. Small fluid-filled sacs called bursa cushion the joint and help reduce friction between the muscles and other surrounding structures.

The bones that make up the knee joint.

In adults, Baker’s cysts usually result from an injury or condition that causes swelling and inflammation inside the knee joint, such as:

  • Osteoarthritis
  • Rheumatoid arthritis
  • Meniscus tear
  • Anterior cruciate ligament (ACL) tear
  • Other conditions that damage the tissues inside the joint

In response to this inflammation, the knee produces excess synovial fluid, which travels behind the knee and accumulates in the popliteal bursa. The bursa then swells and bulges, forming a Baker's cyst.

In younger patients, Baker’s cysts often have no known cause.

A cyst forms when excess synovial fluid travels to the popliteal bursa at the back of the knee.

Some Baker’s cysts cause no symptoms and are only discovered incidentally during a physical exam or when an MRI scan is performed for some other reason. When symptoms do occur, they may include:

  • A feeling of fullness or a lump behind the knee
  • Knee pain
  • Stiffness or tightness at the back of the knee
  • Swelling in your knee and lower leg

If the cyst becomes very large, it can interfere with blood flow in the veins of your leg. This can cause pain, swelling, weakness, or even numbness if there is nerve compression. Very rarely, the cyst can even burst.

Sometimes the symptoms of a cyst may resemble those of a blood clot or deep vein thrombosis, a much more serious problem. If you have increasing pain and swelling in your calf, it is important to seek medical care right away to rule out a blood clot.

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Medical History and Physical Examination

Your doctor will take a full medical history and ask you to describe your symptoms. He or she will want to know if you have had a previous knee injury.

Your doctor will then perform a careful examination of your affected knee, comparing it to your “normal” knee. During the exam, he or she will look for:

  • Swelling
  • Instability of the joint
  • A clicking or popping noise when you bend your knee
  • Joint stiffness and limited range of motion

Your doctor will also palpate (feel) the back of your knee where the cyst is located. Often, a cyst will become firm when the knee is fully extended and soft when the knee is bent.

Imaging Tests

Imaging tests may be ordered to help confirm the diagnosis and provide more information about your condition.

X-rays. X-rays provide images of dense structures, such as bone. Although a cyst cannot be seen on an x-ray, one may be ordered so that your doctor can look for narrowing of the joint space and other signs of arthritis in the joint.

(Left) In this x-ray of a normal knee, the space between the bones indicates healthy cartilage. (Right) This x-ray of an arthritic knee shows severe loss of joint space.

Ultrasound. This test uses sound waves to create images of structures inside the body. An ultrasound will help your doctor see the lump behind your knee in greater detail and determine whether it is solid or filled with fluid.

Magnetic resonance imaging (MRI) scans. These tests produce clear pictures of the body’s soft tissues. Your doctor may order an MRI scan to learn more about your cyst and to look for a meniscus tear or another underlying condition.

This MRI scan shows an area of fluid behind the knee, the characteristic location of a Baker’s cyst.

Nonsurgical Treatment

Most Baker’s cysts will go away on their own. For cysts that do not disappear, initial treatment is always nonsurgical in nature and may include one or more of the following:

  • Observation. Your doctor may recommend simply observing the cyst over time to ensure that it does not grow larger and cause painful symptoms.
  • Activity modification. Decreasing your activity and avoiding high-impact activities that irritate the knee, such as jogging and aerobics, can help alleviate symptoms.
  • Nonsteroidal anti-inflammatory medications.  Drugs like ibuprofen and naproxen can help reduce pain and swelling.
  • Steroid injection. Your doctor may inject a corticosteroid medication into your knee joint to reduce inflammation.
  • Aspiration.  In this procedure, your doctor numbs the area around the cyst, then uses a needle to drain the excess fluid from the joint. Aspiration is often performed using ultrasound to guide the placement of the needle.

Surgical Treatment

Surgical treatment for a Baker’s cyst is rarely needed. However, it may be recommended if you have painful symptoms that are not relieved with nonsurgical treatment or if your cyst returns repeatedly after aspiration.

Arthroscopy. In this procedure, your doctor makes tiny incisions under anesthesia, then inserts a small camera called an arthroscope into the knee joint. The camera displays images on a video screen and your doctor uses these images to guide miniature surgical instruments.

Arthroscopy is used to treat conditions inside the knee, such as meniscus tears, that may give rise to a Baker’s cyst.

Photo shows a camera and instruments inserted through portals in the knee.

Excision. For large cysts or those that are causing nerve and vascular problems, your doctor may perform an open surgical procedure to excise (remove) the entire cyst.

It is very important to follow your recovery instructions to prevent the recurrence of a Baker's cyst.

Early movement. If your cyst has been aspirated or if you have had arthroscopic surgery, you will most likely be allowed to walk right after the procedure, but you should avoid strenuous activity during your recovery.

Bracing. Your doctor may recommend that you wear a knee brace for several weeks after surgery to immobilize your knee.

Physical therapy. Specific exercises will help improve range of motion and strengthen the muscles around the knee.

The time it takes to recover from surgery varies from patient to patient, depending on whether the underlying condition in the joint was treated during the procedure. Most patients can expect a return to full activity around 4 to 6 weeks after surgery.

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Baker's cyst treatment - Orthopedics Ruslana Sergienko

Baker's cyst (Becker, popliteal cyst) is the result of an inflammatory process of the mucous intertendon bags between the tendons of the middle head of the gastrocnemius and semimembranosus muscles. Such intertendon mucous bags are a developmental variant and exist in half of healthy people. The disease develops only when an inflammatory process develops in these bags, accompanied by an increase in bags in size, pain and impaired movement in the knee joints.

CAUSES OF BAKER'S CYSTS (Becker, popliteal cyst)

The cause of inflammation is inflammatory diseases of the knee joint itself: diseases of the meniscus, deforming osteoarthritis.
Mucous tendon bags have a connection with the cavity of the knee joint through a narrow slit-like opening. With inflammation of the inner lining of the knee joint, the inflammatory fluid from the joint cavity enters the bag, accumulates there and causes the formation of a cyst. The cyst has a special valve (the so-called plug), which prevents the backflow of fluid from the cyst into the joint cavity.


The cyst is a dense elastic formation of a rounded shape in the upper corner of the popliteal fossa, somewhat displaced inwards. When probing, pain is felt.

To clarify the diagnosis, an ultrasound examination of the knee joint or magnetic resonance imaging (MRI) is performed.

An ultrasound revealed a Baker's cyst.

MRI view of a multilocular Baker's cyst.


The most common complication of a Becker's cyst is its rupture, with fluid from the cyst penetrating into the abdomen of the gastrocnemius muscle. This complication develops in every 10 patients with a Baker's cyst. The rupture of the Baker's cyst is manifested by a thickening of the calf, redness, local fever, pain and swelling along the back of the leg may appear.

Due to its anatomical location, Baker's cyst can serve as a factor in obstructing the outflow of blood through the veins of the leg, inflammation of the walls of the veins (thrombophlebitis) with further blockage of the lumen of the vein by a blood clot (thrombosis).
Naturally, when bending the knee joint, for example, when squatting, the cyst and the soft tissues surrounding it are squeezed. There is pain, the person cannot sit down completely.
In some cases, it is possible to deposit calcium salts in the cyst itself, as a result of which the cyst thickens, the patient begins to "feel" it more strongly, the cyst squeezes the surrounding tissues more, causing serious threats to the patient's health.


Non-surgical treatment

Non-surgical treatment of a cyst consists in treating the disease that led to its formation. Usually these are inflammatory diseases of the joints, which provide the necessary "substrate" for filling the cyst with inflammatory fluid.
Until recently, the treatment for a Baker's cyst was to puncture the cyst. The cyst was pierced with a puncture needle, the liquid was removed, and hormonal preparations - glucocorticosteroids - were injected into the cyst cavity.
However, to date, this method of treatment is considered ineffective, since some time after the puncture, fluid is again collected in the cyst, which enters it from the joint cavity, and it cannot go back because of the valve, which allows fluid to pass through only one direction - from the joint cavity to the cyst. Therefore, the only way out in this situation is to eliminate the valve, and this is possible only by removing the valve using arthroscopy.

Surgical treatment

Previously, the standard of surgical treatment was removal of the cyst. A long incision of 10-15 centimeters was made in the popliteal region above the cyst. Carefully separating the soft tissues of the popliteal region (to avoid damage to the popliteal vessels and nerves), a cyst was isolated. The junction of the cyst with the cavity of the knee joint was sutured, bandaged, and the cyst was cut off.

Such operations are quite traumatic for patients, require a long stay in the hospital (7 or more days), are often accompanied by the formation of painful scars in the popliteal region, more serious rehabilitation, and longer recovery times after surgery.

Removal of a cyst using arthroscopy

Arthroscopy is the most modern and "low-traumatic" method of surgical treatment of Baker's cyst.

Baker's cyst exercises and remedies

A Baker's cyst, also known as a popliteal cyst, is a sac of fluid that forms behind the knee.

Baker's cysts tend to feel hard when the knee is fully extended and soft when the knee is bent. Physiotherapists call this change in density the Foucher sign.

Most Baker's cysts do not cause symptoms. Usually, a person becomes aware that he is only when a doctor detects him as part of a routine examination or test for another issue.

However, this type of cyst can cause pain or swelling that can restrict movement.

Baker's cysts sometimes resolve without treatment. A doctor is unlikely to recommend medical intervention unless the cyst is causing discomfort or difficulty moving the knee.

A number of medications and exercises can help reduce any symptoms of Baker's cysts and prevent them from forming. Keep reading to find out more.

Exercises to maintain range of motion of the knee can relieve pain and prevent muscle weakness.

However, before attempting any Baker's cyst exercise, talk to your doctor or physical therapist. Incorrect exercise can damage the knee, making the pain worse.

The following exercises can help a person with a Baker's cyst:

Standing calf position

  1. Stand directly in front of a chair or other heavy piece of furniture, and use it for balance if needed.
  2. Step back with your right foot, then bend both knees until a stretch occurs.
  3. Hold this stretch for 20 seconds, then switch sides.

Heel Raise

  1. Sit in a chair with both feet on the floor and knees at a 90 degree angle.
  2. Raise one heel while keeping the foot on the floor.
  3. Press on the top of the knee to flatten the leg. Repeat this 10 times, then switch to the other side.

calf stretch

  1. Sit on the floor with your legs straight out in front of you.
  2. Hook the towel or exercise band under the foot pads, then gently pull back.
  3. Hold stretch for 10 seconds, then switch sides.


Baker's cysts often form as a result of knee injury. During recovery, walking can help a person gradually gain strength and mobility.

However, if a person needs to change their gait or bend their knee into an unusual position in order to walk comfortably, they may not be safe to walk yet. Consult a doctor or physiotherapist.

The following home care strategies may help relieve the symptoms of a Baker's cyst or prevent it from forming:

  • Apply ice packs or ice packs to the cyst to reduce pain and swelling.
  • Apply heat to the area. Some people find that alternating ice and heat works well.
  • Take non-steroidal anti-inflammatory drugs such as acetaminophen or ibuprofen.
  • Avoid any activity that causes pain. If walking is painful, use crutches to relieve pressure on the injured knee.
  • Gently massage the area around the cyst to relieve pain and help reduce inflammation.

Baker's cyst often appears after a knee injury. Therefore, preventing knee injuries is the best way to prevent these cysts from developing.

To avoid knee injury:

  • Wear supportive shoes that fit well.
  • Warm up before training and sports, then cool down.
  • Refraining from knee exercises is already tender and painful.
  • Seek treatment for any knee, leg or foot injury - an injury to one area of ​​the body can increase the risk of falls and further harm.

The knee, like other joints, contains fluid-filled sacs called bursae. The fluid helps lubricate the joint so it can move smoothly.

When the knee secretes too much of this fluid, the bursa can swell, causing a Baker's cyst to form. These cysts can be painful and make it difficult for the knee to move.

Baker's cysts usually appear after an injury such as a fall. They can also develop in people with chronic joint disease. Sometimes there is no clear reason.

Anyone can get a Baker's cyst, but they are more common in children aged 4-7 years and adults aged 35-70 years.

Risk factors include:

  • Abuse and injury: Injury such as falls or sudden blows and chronic overuse can cause these cysts. They often form when the cartilage of the knee is torn.
  • Inflammatory joint disease: People with rheumatoid arthritis and osteoarthritis may be more likely to develop these cysts.

Even if a Baker's cyst is not causing symptoms, it is important to see a doctor for an accurate diagnosis.

Other conditions, including deep vein thrombosis, a dangerous blood clot, may mimic the features of a Baker's cyst.

It is also important to see a doctor if:

  • The cyst appears to be growing.
  • The cyst becomes painful.
  • The cyst makes it difficult to walk or move the knee.
  • Treatment stops working.
  • Symptoms worsen.
  • The cyst causes numbness in the knee or leg.

Pain or numbness can occur when cysts become large enough to press on surrounding structures, damaging blood vessels or nerves.

Learn more

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