What is a Baker's cyst?

A Baker's cyst, or popliteal cyst, is a build-up of fluid or swelling behind your knee. It's usually caused by excess fluid that comes from your knee joint.

A Baker's cyst can cause pain and swelling behind your knee. Often it won't cause any symptoms.

A Baker's cyst can be caused by arthritis, or a knee injury such as a torn meniscus. It may also develop for no reason.

What are the symptoms of a Baker's cyst?

If the Baker's cyst is small you may not have any symptoms.

Symptoms may include:

• pain
• swelling
• a lump behind your knee
• pressure when you bend your knee
• being unable to fully straighten your knee
• pain in your calf
• clicking in your knee

You may find your symptoms are worse after walking or being active.

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What are the causes of a Baker's cyst?

Common causes of a Baker's cyst include:

• injury to your knee — torn cartilage and torn meniscus
• arthritis — rheumatoid arthritis and osteoarthritis
• infection — tuberculosis
• gout

A Baker's cyst can develop for no reason.

When should I see my doctor?

You should see your doctor if you have symptoms of a Baker's cyst.

When to seek urgent care?

Pain and swelling in your leg can be a sign of deep vein thrombosis (DVT), which is a serious medical condition. You should get urgent care if:

• you have leg pain or swelling that quickly gets worse
• the skin on your leg feels warm
• the skin on your leg becomes red or dark
• you have leg pain as well as chest pain

See your doctor immediately if you have signs of a deep vein thrombosis (red, swollen leg).

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How is a Baker's cyst diagnosed?

A doctor can usually diagnose a Baker's cyst by examining your knee and asking about your symptoms.

They might arrange for you to have imaging of your knee, to check for the cause of the Baker's cyst. This may include an:

• ultrasound
• x-ray
• MRI scan

How is a Baker's cyst treated?

Baker's cysts often go away without needing treatment.

Self-care at home

You can help manage your pain and swelling by:

• using paracetamol or anti-inflammatory medicines
• avoiding activities that make your knee sore
• elevating your knee (sitting with your feet up) to limit swelling

Light physical activities such as walking or swimming can help you manage your pain. Discuss your exercise program with a physiotherapist or exercise physiologist before starting.

Other treatment options

If your Baker's cyst is causing you a lot of pain, your doctor may suggest treatment. Treatment options include:

• draining the Baker's cyst to remove swelling
• injecting the Baker's cyst with corticosteroids to help manage your pain
• surgery to repair any damage to your knee joint
  

If the cyst is caused by arthritis or a knee injury, treating these conditions can help.

Talk to your doctor about what treatment is best for you.

What are the complications of a Baker's cyst?

Some possible complications of a Baker's cyst include:

• chronic (long-term) pain and swelling
• claudication (cramping) in your leg
• rupturing (bursting) of the cyst, which causes the contents of the cyst to spread into your calf
• septic arthritis (joint infection)

Most people with a Baker's cyst will not have any complications.

Can I prevent Baker's cysts?

Knee injuries are a common cause of Baker's cysts.

Here are some tips to prevent knee injuries:

• Make sure you warm up and cool down, before and after exercising.
• Wear supportive shoes.
• Be careful when exercising on uneven ground.
• If you hurt your knee, stop what you are doing and speak to a doctor or physiotherapist.

If you have an existing knee injury, speak to your doctor about how to treat it. This can help lower the chance of a Baker's cyst developing.

Resources and support

You can read the Musculoskeletal Health Australia fact sheet about Baker's cysts, or call their helpline and speak to a nurse on 1800 263 265.

The Royal Children's Hospital also has a Baker's cyst fact sheet — it explains how a Baker's cyst can form in children.

You can also call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available to speak with you 24 hours a day, 7 days a week.