Mucous Cyst

This leaflet provides general information to help you understand mucous cysts and the available treatment options.

Not everyone with a mucous cyst needs surgery.

At the heart of my practice is Shared Decision-Making. Whether we pursue conservative management (Plan A) or surgical intervention (Plan B), the goal is to create a tailored treatment plan that aligns with your lifestyle, values, and functional goals.

The Anatomy of a Mucous Cyst

A mucous cyst forms near the joint closest to the fingertip, relying on several structures working together.

How a Cyst Forms

It is an out-pouching of the joint:

• Forms at the last finger joint (the DIP joint)
• The joint lining balloons out into a small sac
• A one-way valve lets it fill with fluid

The Fluid

The sac holds thick, jelly-like fluid that normally lubricates and nourishes the joint — it is not cancerous.

The Link with Arthritis

Mucous cysts go hand in hand with wear:

• Usually seen with osteoarthritis of the joint
• Bone spurs form at the worn joint
• Pressure pushes fluid into the sac
• The cyst sits just under the skin

Effects on the Nail

• A groove can form in the nail
• The skin over the cyst may thin
• The finger can look deformed
• Several fingers can be affected

The Result

Many cause only a small lump, but some are painful, deform the nail or thin the skin, and occasionally drain fluid on their own.

What Is a Mucous Cyst?

A mucous cyst is a fluid-filled sac that usually forms near the joint closest to the fingertip (the DIP joint). It is linked to osteoarthritis and holds thick, jelly-like fluid, and it can sometimes deform the nail or drain on its own.

Common Features

Typically it appears as:

• A small lump just under the skin near the nail
• A groove or ridge in the nail beyond it
• Thin, shiny skin over the top

Why It Happens

It is closely linked to joint wear:

• Osteoarthritis of the fingertip joint
• Bone spurs around the worn joint
• A one-way valve trapping fluid
• Pressure within the joint

Symptoms & Examination

Symptoms

• A visible small lump on the finger near the nail
• Pain in the cyst or the underlying joint
• A groove in the nail or thinning skin

Examination

• The cyst and nearby joint are examined
• The skin over the cyst is checked
• Signs of arthritis in the joint assessed

Diagnosis

• Usually a clinical diagnosis from examination
• X-ray often used to assess the arthritis

Treatment Options: A Shared Decision

I will discuss all available treatment options with you, explaining the benefits and risks of each. Your preferences, values, and lifestyle will be considered as we work together to create a treatment plan best suited to your needs — this shared decision-making process ensures you are fully informed and involved in your care.

Treatment Depends On

• Whether the cyst is painful or deforming
• The state of the skin over the cyst
• How much arthritis is in the joint
• Your preferences and goals

Mucous cysts are not harmful and many need no treatment — if it isn't painful or breaking down the skin, doing nothing is always an option.

Plan A — Non-Surgical

• Observation: often all that is needed if it is not troublesome
• Skin Care: protect the skin and dress it if it bursts
• Antibiotics: used if the skin breaks down or infects
• Aspiration: not routinely advised, as it often returns and risks infection

Plan B — Surgical

Considered when…

• Pain: significant pain, with or without deformity
• Skin: the skin is thin, bursting or repeatedly draining
• Appearance: the cyst is unsightly or deforming the nail
• Options: excision, removal of bone spurs, or joint fusion
• Approach: usually a day case under local anaesthetic
• The Procedure: known as Cyst Excision, the cyst and any underlying bone spur are removed to protect the skin and reduce return, usually under local anaesthetic. A separate leaflet will be provided for the surgery.

Management Pathway

Questions You May Wish to Ask

• What treatments should I try first?
• How long should I try them for?
• What improvement can I expect?
• What happens if I don't have surgery?