Overview
A Baker's cyst (popliteal cyst) is a fluid-filled lump at the back of the knee. It may get better on its own or by treating the condition causing it, but you should get any lumps checked by a GP.
Symptoms of a Baker's cyst
The main symptom of a Baker's cyst is a soft lump at the back of the knee.
The fluid-filled lump may be more visible when standing up.
The lump may be your only symptom, but you may also have:
- knee or leg pain
- tightness, stiffness or aching in your knee
- difficulty bending your knee
- clicking in your knee
Your symptoms may be worse after walking.
See a GP if:
• you have a lump anywhere on your body and you do not know what it is
Ask for an urgent GP appointment or get help from NHS 111 Wales if you have:
- pain or swelling in your leg that suddenly gets worse
- 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 symptoms of a burst cyst (rupture) or blood clot in the leg called DVT (deep vein thrombosis).
You can call 111 or get help from 111 Wales online.
Call 999 or go to A&E if:
You have symptoms like pain and swelling in your leg, and:
- breathlessness
- chest pain
These could be symptoms of a blood clot that has travelled to your lungs (pulmonary embolism).
A pulmonary embolism can be life-threatening and needs to be treated immediately.
Find your nearest A&E
Do not drive to A&E. Ask someone to drive you or call 999 and ask for an ambulance.
Bring any medicines you take with you.
What happens at your appointment
The GP will examine your leg and check for other health conditions that could be causing a Baker's cyst.
They may send you for an ultrasound or MRI scan, or refer you to a specialist for more tests or to rule out any serious causes.
Treatment for a Baker's cyst
A Baker's cyst does not always need treatment. Sometimes, particularly in children, it will get better on its own.
If the Baker's cyst is caused by an underlying condition, your symptoms will usually get better when that condition is treated. But other treatments for a Baker's cyst can include:
- painkillers
- a painkilling injection (hydrocortisone injection) in your knee
- physiotherapy
- draining fluid out of the cyst
- surgery to repair damage to your knee joint – it's rare to have surgery to remove a Baker's cyst
A Baker's cyst can take a few months to a few years to get better.
Things you can do if you have a Baker's cyst
There are things you can do to ease the pain, swelling and other symptoms of a Baker's cyst while it gets better.
They can also help if a Baker's cyst has burst (ruptured). If this happens, your symptoms will be worse than normal until the swelling goes down, which can take a few weeks.
Do
- rest your knee
- gently apply an ice pack (or a bag of frozen vegetables) wrapped in a tea towel to your knee for around 10 minutes at a time, and repeat every few hours if needed
- raise your leg – you can rest it on a pillow
- take ibuprofen or paracetamol to help with pain and swelling
Causes of a Baker's cyst
Sometimes there is no particular cause of a Baker's cyst, especially in children.
In adults they usually happen when another health condition causes damage to the knee joint, like:
Anyone can get a Baker's cyst, but they are more common in people aged 35 to 70.
Treatment
Treatment for a Baker's cyst isn't needed if you don't have any symptoms. Any symptoms you have can be treated at home.
Further treatment will only be needed if the cyst stops you using your knee or causes persistent pain.
Self care
To treat a Baker's cyst you can:
- take non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, to reduce swelling and pain in the affected knee
- hold an ice pack to your knee for 10-20 minutes to reduce any swelling – try a bag of frozen peas wrapped in a tea towel (never put ice directly on your skin)
- rest your knee joint
- wear a knee support – you can buy these from a pharmacy
Further treatment
See your GP for further treatment if your cyst still causes problems after you've tried the self care treatments.
One treatment option is to inject corticosteroid medication directly into the affected knee to help reduce swelling and inflammation.
Treating a ruptured cyst
A Baker's cyst can sometimes rupture (burst), resulting in fluid leaking down into your calf. This causes a sharp pain in your calf, which becomes swollen, tight and red, but redness can be harder to see on brown and black skin.
The fluid will gradually be reabsorbed into the body within a few weeks. The recommended treatment for a ruptured cyst is rest and elevation (keeping the affected calf raised).
Prescription painkillers – usually a combination of paracetamol and codeine – can also be used to control any pain. See your GP for a prescription.
Surgery to repair knee damage
In some cases, it may be possible to drain (aspirate) a Baker’s cyst. However, it may not be possible to aspirate long-term (chronic) cysts because they’re made of jelly.
Surgically removing a Baker’s cyst is not easy because, unlike other types of cyst, they do not have a lining.
Surgery may be needed to repair your knee joint if it's significantly damaged as a result of an injury or a condition such as osteoarthritis.
A type of keyhole surgery called arthroscopy, is usually used. The surgeon will use an instrument called an arthroscope to look inside your knee joint. Small surgical instruments can be used alongside the arthroscope to repair any damage.