Baker's Cyst

What is a Baker's cyst?

A Baker's cyst is a lump filled with fluid that appears at the back of your knee. It's sometimes called a popliteal cyst. The lump is soft and may be more noticeable when you're standing up.

What does it feel like?

The main sign is a soft lump behind your knee. You might also notice:

• Pain in your knee or leg
• Your knee feeling tight, stiff or achy
• Trouble bending your knee
• A clicking sound when you move your knee

These symptoms often get worse after you've been walking or moving around.

When should you see your GP?

You should speak to your GP if:

• You find any lump on your body and don't know what it is

Get urgent help from your GP or call NHS 111 if you have:

• Sudden worsening pain or swelling in your leg
• Swelling, bruising and warm skin on your leg
• Red or darkened skin on your leg (this can be harder to see on brown or black skin)
• Swelling in your leg that gets harder or softer

These could be signs that the cyst has burst or that you have a blood clot in your leg called DVT (deep vein blood clot).

Call 999 or go to A&E immediately if you have:

• Leg pain and swelling along with breathlessness
• Leg pain and swelling along with chest pain

These could mean a blood clot has travelled to your lungs, which is life-threatening and needs emergency treatment.

What causes a Baker's cyst?

Sometimes there's no clear reason why a Baker's cyst develops, especially in children. In adults, they usually happen when something damages the knee joint, such as:

• A knee injury
• Joint wear and tear (osteoarthritis)
• Joint swelling (rheumatoid arthritis)
• Gout

Anyone can get a Baker's cyst, but they're more common in people aged 35 to 70.

How is it treated?

Not all Baker's cysts need treatment. Sometimes, especially in children, they get better on their own. If another health condition is causing your cyst, treating that condition usually helps your symptoms.

Other treatments might include:

• Painkillers
• A painkilling injection in your knee
• Physiotherapy
• Draining the fluid from the cyst
• Surgery (very rarely needed)

A Baker's cyst can take anywhere from a few months to a few years to get better.

What can you do at home?

While your cyst is getting better, you can:

• Rest your knee - avoid activities that make it worse
• Use ice - wrap an ice pack or bag of frozen vegetables in a tea towel and put it on your knee for 10 minutes at a time, every few hours
• Raise your leg - rest it on a pillow when sitting or lying down
• Take painkillers - ibuprofen or paracetamol can help with pain and swelling

If your cyst bursts, your symptoms will be worse than usual for a few weeks until the swelling goes down. The same home treatments can help during this time.

Remember, if you're worried about any symptoms or if they get worse, speak to your GP for advice.

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Based on NHS.uk guidance. Written by Dr Krishnan Pasupathi, NHS GP.