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Baker's cyst

Baker's cyst is a fluid-filled (non-cancerous) lump or swelling behind your knee which causes knee pain.

What is Baker's cyst?

A Baker’s cyst (also known as a popliteal cyst) forms when tissue at the back of your knee fills with synovial fluid – the lubricating fluid from your knee joint. This makes it swollen and inflamed.

Cysts can vary in size and can, very occasionally, develop behind both knees at the same time.

Baker’s cyst is much more common in adults than children, with more women than men affected.

How to tell if you have Baker's cyst

In some cases there are no symptoms, but an MRI scan for another reason finds the cyst. However, the larger the cyst, the more likely it is that you'll notice symptoms other than the swelling itself.

These symptoms can include:

  • A build-up of fluid around your knee
  • Crepitus (a clicking noise in your knee)
  • An ache behind your knee and in your calf
  • Difficulty bending your knee
  • Tightness at your knee joint

Occasionally a Baker’s cyst ruptures which can be painful, with swelling and redness in your calf and may become infected.

Talk to your doctor if you’re concerned about symptoms

You can book an appointment with a Spire private GP today.

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Diagnosis and tests for Baker's cyst

Your GP will examine your knee and ask questions about the swelling and how you’re feeling.

You'll usually get a diagnosis from your GP without any further tests. However, in some cases you might have an ultrasound scan or MRI scan. This is to rule out other causes, eg deep vein thrombosis (DVT) or an aneurysm (a bulge in a blood vessel), or to check the extent of the cyst.

A child may be referred to a specialist paediatric orthopaedic surgeon if there’s the possibility of an underlying joint disease.

Causes of Baker's cyst

You're more likely to develop Baker's cyst if you have an underlying problem with your knee. The most common cause of Baker’s cyst in adults is osteoarthritis and rheumatoid arthritis.

It can also affect people who have gout.

Other possible causes of Baker’s cyst include a sports-related injury such as:

  • A meniscus tear
  • Anterior cruciate ligament damage
  • Cartilage damage

In children, the cyst may relate to injury or irritation of the bursa. Cysts may also occur with conditions such as juvenile idiopathic arthritis.

Common treatments for Baker's cyst

There are things you can do yourself to treat Baker’s cyst including rest and taking ibuprofen or paracetamol, if advised by your doctor.

In many cases the swelling goes away by itself. Using compression bandages and an ice pack can also help.

A cyst may sometimes be aspirated. This means a fine needle is inserted to remove fluid. In some cases, surgery may be recommended to repair damage around the joint.

If there’s an underlying condition, treating it will usually shrink the cyst.

Other treatments related to Baker’s cyst include:

  • Knee arthroscopy
  • Knee joint repair
  • Steroid joint injections