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Ganglion - synovial cyst

A ganglion, ganglion cyst, or synovial cyst, is a swelling filled with fluid near a joint or tendon, such as the wrist, hand or fingers.

The swelling looks like a smooth soft lump under the skin and can range from pea-sized to being as big as a golf ball in some cases.

The swelling contains a jelly-like substance called synovial fluid.

Ganglion cysts do not always cause any pain unless they are next to a nerve.

Pictures of ganglions

A traumatic ganglion. This person came to the accident and emergency department with a painful bump after the wrist was hit by a car door.

ganglion cyst 1

The jellylike fluid taken from the cyst in image 1. Its presence confirms the diagnosis of a ganglion.

ganglion cyst 2

An ultrasound image shows the ganglion (area between markers) from image 1.

A ganglion that has been operated on in the past. This ganglion returned because this person plays the cymbals in her school band.

Ganglion causes

The cause of ganglion cysts is not known. One theory suggests that trauma causes the tissue of the joint to break down forming small cysts, which then join into a larger, more obvious mass. The most likely theory involves a flaw in the joint capsule or tendon sheath that allows the joint tissue to bulge out.

Ganglion symptoms


  • The ganglion cyst swelling may appear over time or appear suddenly, may get smaller in size, and may even go away, only to come back at another time.
  • Ganglions can cause some degree of pain, usually following acute or repetitive trauma, but many are without symptoms, except for appearance.
  • Any pain is usually nonstop, aching, and made worse by joint motion.
  • When the ganglion is connected to a tendon, there may be a sense of weakness in the affected finger.

When to seek medical care

If the ganglion cyst is causing pain, or if you have concerns, seek medical advice.

A doctor will be able to advise on whether the ganglion cyst is a cause for concern or whether treatment is needed.

Examinations and tests

A physical examination is often all that is needed to diagnose a ganglion.

  • Your doctor may get further confirmation by having a sample of fluid in the cyst tested. An ultrasound scan may be arranged to determine whether the bump is fluid-filled (cystic) or if it is solid. Ultrasound can also detect whether there is an artery or blood vessel causing the lump.
  • Your doctor may send you to a hand surgeon if the bump is solid or involves a blood vessel (artery).
  • Magnetic resonance imaging (MRI) is used to see the wrist and is very useful for ganglions.
  • If the ganglion cyst is not causing significant pain or discomfort, the NHS may not provide treatment, classifying removal of the cyst as a cosmetic procedure.


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