Bakers Cyst

Choose a category

Summary

  • The knee contains sacs of fluid called bursa that help to cushion the joint and reduce friction between the structures around it
  • A Baker's cyst is a pronounced swelling on the back of the knee, caused by the abnormal collection of fluid inside the bursa
  • Treatment may include physiotherapy treatment, drawing off the fluid with a needle, cortisone injections, treating the underlying cause or surgery to remove the cyst.

On this page

A Baker's cyst is a swelling on the back of the knee caused by the build-up of fluid inside sacs called bursa between the two heads of the gastrocnemius (calf muscle). The symptoms are usually mild unless in the rare situation the cyst bursts or extends down into the calf muscles. A Baker's cyst is also known as a popliteal cyst.

bakers cyst image

The knee is a hinge joint between the thigh bone and shin bones. The entire joint is enclosed inside a tough capsule lined with a membrane and filled with lubricating synovial fluid. Extra capsules or sacs of fluid, known as bursa, cushion the joint and help reduce the friction between tissues caused by movement.

When the knee produces too much synovial fluid, the excess fluid causes the bursa behind the knee to expand and bulge. Common causes of Baker's cyst include arthritis, infection, torn knee cartilage and other knee injuries. 

Back to top

Symptoms of a Baker's cyst

Often there are no symptoms and the cyst can remain unnoticed. If symptoms do occur, they can include:

  • a pronounced soft lump or swelling on the back of the knee that looks most obvious when the person is standing
  • a sensation of pressure in the back of the knee joint
  • persistent pain or aching
  • restricted mobility of the knee joint
  • a sensation of tightness at the back of the knee when the leg is straightened.

Back to top

Causes of a Baker's cyst

Some of the common causes of Baker's cyst include:

  • injury - trauma or injury to the knee that can cause a build-up of fluid (effusion), which triggers Baker's cyst
  • torn cartilage - usually affecting the cartilages (known as menisci) that bolster the knee joint on both sides
  • arthritis - particularly rheumatoid arthritis and osteoarthritis of the knee joint
  • infection - which locally can cause fluid retention around the knee joint
  • unknown causes - Baker's cysts can sometimes develop in children for no apparent reason.

Back to top

Complications of a Baker's cyst

A person may be less inclined to seek medical help for a Baker's cyst if the symptoms are mild, which they generally are. However, if left untreated, complications can develop that may include:

  • the cyst continues to grow, causing the symptoms to worsen
  • the cyst may extend down into the calf muscles (dissection)
  • the cyst may burst and cause bruising on the ankle of the affected leg, due to leaked fluid

The symptoms of calf dissection and cyst rupture are similar to those caused by inflammation of veins, which may make diagnosis difficult and delay treatment. It is important to seek medical advice, as more serious but less common problems can present in a similar way. These may include a tumour, deep vein thrombosis or popliteal artery aneurysm. 

Back to top

Diagnosis of a Baker's cyst

A Baker's cyst is diagnosed using a number of tests, including:

  • physical examination
  • medical history
  • joint x-ray - this will not show the cyst, but can show the presence of arthritis in the knee joint that may be causing the problem
  • shining a light through the cyst (transillumination) - this can determine that the mass is filled with fluid
  • magnetic imaging resonance (MRI)
  • ultrasound.

Back to top

Treatment for Baker's cyst

Baker's cysts don't always require active treatment as they can resolve on their own. Sometimes they will only require observation over time by the treating doctor.

If treatment is required, options for treatment can include:

  • treatment of the underlying cause, such as medication for arthritis or surgery for torn knee cartilage
  • temporarily avoiding activities that aggravate the knee joint
  • physiotherapy, which may comprise of activity modification advice, heat or ice treatment, the use of crutches, and exercises to maintain mobility and strength of the knee
  • cortisone injections to reduce inflammation in the knee joint
  • inserting a needle into the cyst and draining off the fluid if the cyst is large enough
  • in severe cases, surgery to remove the cyst entirely if conservative treatments are ineffective
  • a conservative approach of watching and waiting is recommended with children - the condition commonly subsides on its own without active treatment.

Back to top

Prevention of a Baker's cyst

Knee joints are prone to injury during sporting activities. Preventing knee trauma can reduce the risk of a Baker's cyst developing in the first place or recurring after treatment.

Suggestions include:

  • warm up the knee joints and soft tissue by gently going through the motions of your sport or activity, and stretching the muscles before commencing your sport or activity
  • wear supportive footwear appropriate to your activity
  • try to turn on the balls of your feet, rather than through your knees to help avoid knee injuries
  • cool down after sport by performing gentle and sustained stretches
  • if you injure your knee, stop your activity immediately, apply ice packs to treat the swelling and seek medical advice.

Back to top

Where to get help

  • Your doctor
  • Sports medicine professional
  • Physiotherapist
  • MOVE muscle, bone & joint health
    Help Line: Tel. 1800 263 265

Back to top

Things to remember

  • The knee contains sacs of fluid called bursa that help to cushion the joint and reduce friction between the structures around it.
  • A Baker's cyst is a pronounced swelling on the back of the knee, caused by the abnormal collection of fluid inside the bursa.
  • Treatment may include physiotherapy treatment, drawing off the fluid with a needle, cortisone injections, treating the underlying cause or surgery to remove the cyst.

Back to top

More information

  • Need medical information regarding your condition and commonly prescribed treatments? Or assistance navigating the health, disability and social services systems? Contact the nurses on our Help Line on 1800 263 265 or email helpline@move.org.au.
  • Interested in finding out about our upcoming webinars and seminars and other events. Click here to learn more. 

Download a PDF of this information.


This information has been provided by the Better Health Channel and has been produced in consultation with and approved by: MOVE muscle, bone & joint health.

Move - muscle, bone and joint health, the new voice of Arthritis Victoria

Welcome to MOVE muscle, bone & joint health, the new voice of Arthritis and Osteoporosis Victoria.

We may have a new name but since 1968 we have been the leading provider of supported solutions and trusted knowledge to the one-in-three Australians who live with these conditions.

continue to site