A knee pit cyst or Baker’s cyst indicates a small, often painless swelling in the hollow of the knee, which is often caused by an underlying condition in the knee, for example due to knee osteoarthritis or because the knee ligament has been torn or the cartilage has been damaged. The result is a tight feeling in the back of the knee and bending the knee is difficult. The swelling usually does not hurt. The complaints increase with exertion. Treatment often consists of addressing the underlying condition. A knee pit cyst does not normally occur on its own. Exercise therapy (physiotherapy) for knee pit cyst or Baker’s cyst ensures that you keep moving without forcing anything. Surgery is rarely necessary for a cyst in the popliteal fossa. A knee pit cyst is most common in children aged 4 to 7 years and in adults aged 35 to 70 years.
- What is a knee pit cyst?
- Causes of a knee pit cyst
- Who gets a Baker’s cyst?
- Symptoms of a knee pit cyst
- Complications of a cyst in the popliteal fossa
- Rupture
- Deep vein thrombosis
- Infection
- Examination and diagnosis
- Treatment of a knee pit cyst
- Treatment of an underlying knee problem
- Treatment to relieve symptoms
- Other treatments
- Prognosis
- Prevention
knee pit cyst / Source: Alila Medical media/Shutterstock.com
What is a knee pit cyst?
A knee pit cyst, also called a Baker’s cyst¹, indicates a small, often painless swelling in the hollow of the knee, which feels like a soft swelling filled with water. It is often a manifestation of another condition in the knee, such as osteoarthritis. The knee joint is filled with synovial fluid, also called synovial fluid. If there is too much fluid, the joint cavity (synovial cavity) can expand backwards through openings in the posterior capsule and form a cyst there. This cyst is called a knee pit cyst. Swelling in the hollow of the knee hinders bending of the knee. When you are active, this can hurt.
Causes of a knee pit cyst
The development of a knee pit cyst is often a manifestation of another condition of the knee. When a joint is damaged, it produces more fluid, which then spreads to the popliteal fossa through one of the openings of the posterior capsule, causing swelling. The knee joint can be irritated by, among others, the following causes:
- trauma or injury to the knee, for example: the knee is bruised, the knee ligament is torn or the cartilage is damaged (torn meniscus);
- arthritis, especially rheumatoid arthritis;
- osteoarthritis of the knee joint (in osteoarthritis the cartilage changes with complaints such as stiffness and joint pain);
- infection;
- unknown causes (sometimes a knee pit cyst develops in children for no apparent reason).
Who gets a Baker’s cyst?
A Baker’s cyst is most common in children aged 4 to 7 years and in adults aged 35 to 70 years. However, a knee pit cyst is much more common in adults than in children. You are more likely to develop a knee pit cyst if you have an underlying problem with your knee. Arthritis is the most common condition associated with a knee pit cyst. This may involve different forms of arthritis, such as osteoarthritis, rheumatoid arthritis, psoriatic arthritis and gout. A knee pit cyst can also develop if you have (had) a torn meniscus or if there is something wrong with one of the ligaments in the knee, or if you have had an infection in your knee joint.
Symptoms of a knee pit cyst
A knee pit cyst can cause the following symptoms and complaints:
- a swelling in the back of the knee, which can vary in size from day to day;
- the swelling usually does not hurt;
- you may experience a throbbing sensation in the back of your knee;
- limited mobility of the knee joint;
- a feeling of tightness at the back of the knee when the leg is straightened.
A ruptured Baker’s cyst (a rupture) can cause symptoms that resemble a thrombosed leg.
Complications of a cyst in the popliteal fossa
Rupture
The most common complication of a knee pit cyst is rupture. If this happens, fluid from the cyst can leak into your calf muscle. This can cause swelling in your calf. You may also experience itching, due to irritation caused by the fluid leaking from the cyst. About 1 or 2 out of 20 Baker’s cysts rupture.
Deep vein thrombosis
If a knee pit cyst ruptures, it can be very difficult to tell the difference between a ruptured cyst and a deep vein thrombosis (DVT). A DVT is a blood clot that forms in a vein in your leg. In these cases it is important that investigations are carried out to rule out DVT as it is a serious condition that requires treatment.
Infection
In very rare cases, a Baker’s cyst can become infected.
MRI scan / Source: Istock.com/© james steidl
Examination and diagnosis
A knee pit cyst is diagnosed using a number of tests, such as:
- physical examination;
- anamnesis (what a patient can tell the doctor regarding the medical history and relevant circumstances of his complaint);
- X-ray examination for internal injuries of the knee joint;
- an MRI scan of the knee can be made to investigate whether there is damage in the knee (tendons, capsular structures, joint discs, muscle attachments and cartilage can be clearly visualized using this technique);
- ultrasound.
Treatment of a knee pit cyst
Usually, a knee pain disappears on its own. Since a knee pit cyst is usually not the cause of the production of synovial fluid, it is important to detect and treat the underlying cause. The doctor will investigate why your knee produces so much joint mucus and what can be done about it. If the cause is effectively addressed, the cyst will usually disappear on its own. Surgery is rarely necessary and not very successful. Regularly tensing the calf muscles can help to promote recovery. Exercise therapy should preferably take place under the supervision of a physiotherapist, to prevent one-sided training, which would cause other complaints.
Treatment of an underlying knee problem
It is important that any underlying knee problem is treated in the event of a knee pit cyst. This can help reduce the size of the cyst and reduce swelling or pain. In case of osteoarthritis, a steroid injection in the knee can help relieve pain and inflammation. However, this does not mean that the cyst cannot come back. In the event of an injury to the knee, such as a meniscus tear, treatment of this problem can help relieve the symptoms of a knee pit cyst.
Abdominal pain due to NSAIDs / Source: Andrey Popov/Shutterstock.com
Treatment to relieve symptoms
If you are experiencing pain and discomfort as a result of the knee pit cyst, one or more of the following measures may be helpful:
- Non-steroidal anti-inflammatory drugs (NSAIDs). These can help relieve pain and can also limit inflammation and swelling. There are many types and brands. Ibuprofen is freely available at drugstores and pharmacies, so without a prescription. You may need a prescription for some other NSAIDs. Side effects sometimes occur when using NSAIDs. Abdominal pain and bleeding from the stomach are the most serious. Some people with asthma, high blood pressure, kidney failure and heart failure should not take NSAIDs. Therefore, contact your doctor or pharmacist before using NSAIDs.
- Stronger pain relief. If the cyst breaks open, fluid from the cyst may leak into the calf and cause severe pain. In this case, stronger medications may be needed. Ask your doctor for advice.
- Ice can also help reduce swelling and pain. Apply ice to the knee surrounding the cyst. Do not place ice directly on the skin. A washcloth or something similar should be placed in between to prevent frostbite of the skin. You should cool your knee as soon as possible if it starts to hurt. Ice reduces swelling and inflammation. Apply the ice for 10-30 minutes. Less than 10 minutes has little effect. More than 30 minutes can damage the skin.
- Stools. It may be necessary to use crutches until the symptoms have subsided. They help to relieve the strain on the affected leg while you walk.
- Physiotherapy. Keeping your knee joint moving and using strengthening exercises to work the muscles around your knee can be helpful.
Other treatments
There are a number of other treatments that are sometimes used:
- Drainage: Sometimes the doctor may use a needle to drain excess fluid from your knee joint to relieve symptoms.
- Cortisone (steroid) injection: This is sometimes used after fluid drainage to reduce pain and inflammation.
- Surgery to remove the cyst: this happens sometimes, especially if a cyst is very large or painful and/or if other treatments don’t work.
Prognosis
Sometimes a Baker’s cyst disappears on its own. However, if the cyst is large and causing pain, the doctor may recommend treatment. It is often best to treat the cause of the knee problem to get rid of the cyst and prevent it from coming back.
Prevention
Preventing knee injuries is the best way to prevent a knee pit cyst. The following measures can help with this:
- Wearing good and supportive footwear.
- Use the balls of your feet to turn instead of your knees.
- Make sure you warm up properly before exercising and cool down afterwards. A cool-down is the reverse of a warm-up and often consists of a combination of gentle cardio and some stretching exercises.
- Stop immediately if you have a knee injury. It is important to cool, rest and elevate the affected leg when this happens.
Note:
- The knee pit cyst was first described by Dupuytren in 1829. Baker described the cyst in 1877 and since then it has also been called the Baker’s cyst.
read more
- Knee pain: stabbing, burning or aching knee pain
- Pain in the back of the knee: causes of pain at the back of the knee
- Tendonitis: tendinitis in the shoulder, wrist, knee or thigh
- Patellofemoral pain syndrome: symptoms and treatment
- Osteoarthritis: symptoms, causes, treatment and prognosis
