Ganglion cyst

What is a ganglion cyst?

A ganglion cyst (a ganglion) is a smooth, fluid-filled lump under the skin near a joint or tendon¹. It is benign, meaning not cancer¹. In the foot it is often on top of the midfoot, where jelly-like fluid balloons out through a weak spot in the joint or tendon covering². It is thought to come from wear, not a tumour³. It is commoner in the hand and wrist⁴.

They are usually painless and can go away by themselves⁵; they may be noticeable and can sometimes be painful or limit movement⁶.

What causes a ganglion cyst, and who gets one?

No one knows for certain what causes a ganglion cyst¹⁷. It is thought to form when fluid leaks through a weak spot in a joint or tendon covering and collects in a sac²⁸. These lumps are usually found where an area is under frequent physical stress⁹.

A ganglion can develop after an injury, friction or irritation of the tendon lining, or with arthritis⁵. One theory is that the body forms a kind of internal blister in response to injury or overuse⁷. These are possible contributors, not proven causes.

What does a ganglion cyst feel like, and how is it diagnosed?

A ganglion is usually a smooth, firm lump under the skin, most often on top of the foot¹³. It can be pea-sized to golf ball-sized, and sometimes can't be seen¹. It may change size or disappear³. The skin usually looks and feels normal⁵.

Most cause no symptoms¹. Some hurt when you walk or wear shoes, and a few press on a nerve¹.

Diagnosis is mainly from your history and an examination, including shining a light through the lump¹⁰¹¹. Draining thick, clear gel supports it⁶. Other lumps, such as arthritic changes, gout deposits, fatty lumps or, rarely, a tumour, can look similar, so a clinician checks⁶.

What can I do about a ganglion cyst first?

If your ganglion isn't causing pain, it's usually fine to leave it alone and keep an eye on it (watchful waiting)⁵¹². Treatment is usually only suggested when a ganglion hurts⁵.

Draining the fluid with a needle (aspiration) is a further option, but it often doesn't stop the lump coming back¹³¹⁴. Only a trained clinician should do it, after checking whether the lump arises from a joint or tendon, because of the risk of tendon rupture and nerve injury⁴¹³¹⁵.

If it's sore, a pharmacist can advise on simple pain relief that suits you⁵.

What if watching and waiting isn't enough?

If your ganglion keeps hurting, limits movement or keeps coming back, a doctor or foot and ankle surgical service can discuss surgical removal. It lowers the chance of the lump returning compared with draining, though that mostly comes from wrist ganglia in adults¹⁴. For one ganglion near the knee joint, treating the joint itself lowered it further¹⁶.

Surgery has risks, including nerve injury, and recovery takes time⁴¹⁴. The surgeon needs to know where the lump sits and how it relates to nearby structures before draining or removing it⁴. Draining ganglia on the top of a toe or finger isn't recommended, because of the high risk of joint infection¹³.

Will a ganglion cyst go away, and can I stop it coming back?

The outlook is generally good. Many ganglia settle by themselves, with roughly a third to around 60% doing so⁶⁷¹³. Many wrist ganglia settle on their own, often within a couple of years¹⁰.

If a ganglion comes back, it is more likely after draining than after surgical removal, mostly from wrist ganglia in adults¹⁴. Nothing is proven to prevent a ganglion, because the cause isn't well understood¹.

A lump that returns or grows after treatment shouldn't be assumed to be the same ganglion⁶¹¹¹³.

What can make it serious?

• You have new numbness, tingling, pins and needles or weakness in your foot that has come on gradually.
• A lump on your foot or leg is growing, or looks or feels unusual.
• You have pain at night or at rest that doesn't settle.
• You have had cancer before and notice a new lump, or pain that doesn't settle.
• A joint suddenly becomes hot, swollen and very painful, and you have a fever or feel unwell.
• Numbness or tingling in your foot or leg spreads quickly, or comes with new weakness.