Bakers Cyst Knee

Author: Chloe Wilson - BSc(Hons) Physiotherapy

A Bakers Cyst knee is when there is swelling at the back of the knee which causes pain and stiffness. It was first discovered in the 19th century by Dr William Morrant Baker, and is also known as a popliteal cyst or knee cyst.

The cyst develops when there is swelling in the knee joint. Excess synovial fluid seeps backwards out of the joint and into the popliteal bursa - a small fluid filled sac that sits between the hamstring muscle tendons and knee bones to prevent friction. As the fluid enters the bursa it starts to swell, known as a Bakers Cyst.  The average size of a popliteal cyst is 3cm.

The most common cause of a Bakers Cyst is osteoarthritis with 50% of arthritis sufferers developing a popliteal cyst at some point. However other conditions such as gout or any injury to the knee which produce swelling e.g. a cartilage tear can bring on the condition.

Popliteal cysts are most common over the age of 40 and tend to affect women more than men.

Here we will look at the classic symptoms associated with a Bakers Cyst, the best treatment options and how to prevent the condition from recurring in the future.

Symptoms of a Bakers Cyst

Bakers Cyst knee often causes swelling & pain behind the kne

Any injury to the knee can cause swelling which can seep out of the joint into the popliteal bursa. There may only be minor swelling and often a popliteal cyst is so small you don’t even notice anything.

The first symptom people tend to feel with a bakers cyst is a small bulge behind the knee, a bit like a small water balloon or squashy orange. This can grow and then cause pain behind the knee, tightness and stiffness, especially when you bend and straighten the knee. 

The pain associated with a popliteal cyst tends to get worse with activity or when standing for long periods, easing with rest.

Diagnosing A Bakers Cyst

MRI showing a Bakers Cyst - note the white area at the back of the knee

Diagnosis of a popliteal cyst is usually made by your doctor from what you tell him and what he can see. If there is any doubt the doctor can confirm the diagnosis of a Bakers Knee Cyst by performing an ultrasound or MRI scan.

The symptoms of a ruptured popliteal Ccst can be similar to those of a DVT (blood clot in the leg).  If you experience pain in your calf accompanied by any swelling, redness or heat, see your doctor immediately. 

Treatment Options

There are a number of things that can help to treat a bakers cyst including:

Ice can be useful in reducing the pain and swelling associated with Bakers Knee Cyst

1) Ice 

Ice treatment helps to reduce the swelling which will help to reduce the pain. Click the link to find out how to use it safely and effectively. Visit the ice wrap section to find the best ways to apply ice.

2) Medication

Non-steroidal anti-inflammatory Drugs (NSAIDs) e.g. ibuprofen can help to reduce pain and swelling but should only ever be taken on advice of the doctor due to the potential side effects

3) Stretching Exercises

Tightness in the muscles around the knee can aggravate a Popliteal  Cyst by squashing it and therefore stretches can be a very effective way of resolving the condition. Visit the Bakers Cyst Stretches section to find out what exercises can help

A bakers knee cyst can be aspirated - where a needle is used to remove the excess fluid from the popliteal bursa

4) Aspiration

If the popliteal cyst is large or causing pain behind the knee, the excess fluid can be drained with a needle by your GP. However, the problem often recurs – see Preventing Recurrence below for tips on how to avoid this.

5) Injections

You may be offered a cortisone injection (mixture of steroid and local anaesthetic) by your doctor which works to reduce the swelling and reduce the pain behind the knee. Again, the effects are often short lived.

6) Pulsed Electromagnetic Energy (PEME)

AKA short wave diathermy, this form of electrotherapy can help to reduce the inflammation. This treatment is usually carried out by a physiotherapist. I have found this to be an effective treatment with a number of people suffering from a popliteal cyst.

7) Surgery

In a minority of cases, surgery may be indication. This is usually the case if the popliteal cyst is a result of damage in the knee e.g. a cartilage tear or arthritis

Preventing Recurrence

Bakers Cysts frequently return, especially in people suffering from arthritis.  Knee strengthening exercises and knee stretches can often help to prevent a popliteal cyst returning. The stronger the muscles get, the less force goes through the bones making it less likely that the knee will swell which therefore prevents another knee cyst from developing. This is especially the case when the popliteal cyst has developed due to arthritis.

Visit the knee arthritis section to find out more about the symptoms, diagnosis and treatment of arthritis of the knee.

Possible Complications

Occasionally, a Bakers Knee Cyst bursts. The fluid then leaks down the back of your leg into your calf. This can cause swelling and/or a sharp pain in the calf. The fluid will gradually be reabsorbed into the body but this can take up to a month. Pain medication can be used to alleviate any discomfort.

Common Questions

William Morrant Baker was the doctor who first wrote about Baker's Cyst, back in the 19th century

Where Does The Name Baker Cyst Come From? A Baker’s Cyst gets its name from the surgeon who first wrote about the condition, Dr William Morrant Baker (1838-1896). He was an English physician and surgeon. A baker cyst is also known as a popliteal cyst. It is a fluid filled cyst found at the back of the knee.

Is Baker’s Cyst Dangerous? Whilst it is uncomfortable, Baker’s cyst is typically not dangerous.  It is caused by excess fluid in the knee being pushed out into a small sac called a bursa.  This then grows to the point that it is visible on the back of the knee.  

What Causes A Baker's Cyst To Burst? Excessive swelling or pressure on the bursa can cause a Baker's Cyst to burst. When a Baker's cyst ruptures, the fluid seeps down into the calf causing a sharp pain in the calf. The calf may also become red, swollen and tight. A ruptured baker cyst can be extremely painful.

Is Draining A Bakers Cyst Painful? If a bakers cyst is extremely painful or persistent, your doctor may want to drain the fluid with a needle. It is a fairly painless procedure – just a slight prick as the needle penetrates the skin. You may also be given a steroid injection to reduce swelling. In some cases, the fluid return’s.

How Do You Get Rid Of A Baker's Cyst? To get rid of Baker’s cyst, there are ways of reducing the short term pain including using ice and anti-inflammatory painkillers. To avoid recurrence, strengthening the muscles around the knee is important. Stronger muscles mean less force is put through the bones thus reducing the likelihood of swelling and the cyst returning. 

Want To Know More?

There are other causes of swelling and pain behind the knee besides Bakers Cyst knee. Visit the knee pain diagnosis for help working out what is causing your knee pain. 

Go to Common Knee Conditions or Knee Pain Guide

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