A lump on the finger knuckle joint that appears suddenly can cause concern. It can happen for many reasons, ranging from an inflammatory disease to an infection or, more rarely, a tumor.

Most tumors that affect the hands are benign, meaning they are not cancerous. However, cancerous tumors around a finger joint are possible. For this reason, it is important to seek medical help if the lump does not go away.

This article discusses the causes of a lump in the knuckles, the treatments available, and when it is advisable to seek medical help.

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Several types of lump can develop on a finger joint, with each feeling slightly different. The lump could be:

  • a boil or infection, which may make the skin feel tender, swollen, or warm to touch
  • a bone spur, which will feel hard
  • a cyst, which may feel hard or soft depending on how deep it is
  • toughened tissue, which may feel firm

The type of lump a person has will depend on the cause, which a doctor can diagnose.

Below are some potential causes of a lump on the finger joint. This list is not comprehensive, so a person with this symptom may have a condition that does not appear here.

Ganglion cyst

A ganglion cyst is a lump that develops just under the skin near a joint. The cyst contains a jelly-like synovial fluid, which surrounds joints and tendons to lubricate and cushion them during movement. A ganglion cyst forms when this fluid leaks out and collects in a sac.

Although ganglion cysts can affect any joint in the body, they are most common in the wrists and hands. They are usually harmless, but when cysts press on a nerve, they can cause:

  • pain
  • tingling
  • numbness
  • muscle weakness

Doctors usually only recommend treating cysts when they cause pain or prevent the person from moving their joints. The available treatments include aspiration, in which a doctor drains fluid from the cyst with a needle, or surgery to remove it.

Heberden nodes

Heberden nodes are bony growths in the fingertip joints. When someone has a Heberden node, a doctor can detect a lump in their knuckles by performing a physical examination.

Heberden nodes can occur due to osteoarthritis. If this is the case, a person may also have the following:

  • pain
  • inflammation
  • swelling
  • stiff fingers
  • loss of motion
  • difficulty performing daily tasks, such as opening bottles

Hand osteoarthritis has no cure, but treatment can help manage the symptoms. The available options are:

  • hand exercises
  • hot or cold therapy
  • medication to ease the pain and inflammation in the joint
  • surgery to help relieve pain, correct deformity, or replace the damaged joint

Bouchard nodes

Bouchard nodes are bony growths in the fingers’ middle joints. Similarly to Heberden nodes, they are also a potential sign of hand osteoarthritis.

If osteoarthritis causes Bouchard nodes, a person will likely have similar symptoms to those of Heberden nodes and require the same treatment.

Rheumatoid nodules

Rheumatoid nodules are firm lumps that appear under the skin in up to 20% of people with rheumatoid arthritis (RA), a condition in which the immune system attacks healthy joint tissue.

These nodules usually occur in joints that experience trauma, such as the finger knuckles. They are typically firm and rarely painful. Rheumatoid nodules are usually harmless unless they interfere with daily activities or put pressure on nerves, limiting joint movement.

There is no specific medication to treat rheumatoid nodules. However, a combination of disease-modifying antirheumatic drugs (DMARDs) and biological therapies, such as rituximab, may help reduce the chances of nodules appearing.

If nodules develop during RA treatment, adding anti-inflammatory agents, such as hydroxychloroquine and prednisolone, may help reduce their size. Another option is to inject the medication into or under the nodule.

Smaller nodules may not need treatment. Doctors only recommend surgery when the nodule becomes repeatedly injured or knocked.

Infection

Lumps on or in the finger joints may also appear due to an infection, which could occur after injection, surgery, or another injury. A lump could also be a sign of an abscess.

If the infection occurs inside the joint, it is known as septic arthritis. This serious infection can cause long-term joint damage if a person does not receive treatment. The symptoms include:

  • severe joint pain
  • sudden joint swelling, usually in one joint
  • skin color changes around the joint
  • fever or chills
  • a general feeling of being unwell

If a person has any of the above symptoms, they should seek help from a doctor immediately. Doctors will administer antibiotics.

For septic arthritis, this will involve a hospital stay, as doctors need to administer the antibiotics via an IV line.

Tumor

Tumors can also cause lumps near the knuckles. Tumors can be benign, which means noncancerous, or malignant, which means they are cancerous.

There are many types of tumors; one example is a giant cell tumor of the tendon sheath. This is a benign tumor that usually occurs near the finger joints. It does not typically cause pain, but the slow-growing mass can interfere with joint function.

Typically, doctors can remove this type of tumor with surgery. The doctor will decide on the best treatment depending on the position and size of the tumor and the person’s general health and well-being.

While a person waits for a diagnosis or treatment from a doctor, they may find it helpful to practice self-care to ease their symptoms at home.

It may help to:

  • rest the hand
  • wear a splint or orthotic device to help support the finger joints
  • apply warm or cold compresses
  • take an over-the-counter pain medication, if appropriate

A lump in the knuckles can be harmless, but it can also be a symptom of a condition that needs treatment. It is a good idea to seek medical advice if the lump does not go away, gets bigger, or comes with other new symptoms.

Speak with a doctor as soon as possible if any of the following develop:

Seek emergency help if a joint suddenly swells up and becomes severely painful or other symptoms of illness develop, such as fever, shivers, or changes in skin color.

A lump on the finger knuckle can have many causes, including ganglion cysts, Bouchard’s nodes, RA, septic arthritis, or a tumor.

Treatment will depend on the cause and severity of the symptoms. Some people may not need treatment, while others may require medication or surgery to remove the lump.

People should seek medical advice if they notice a lump in the knuckles that does not go away or if they have pain, stiffness, or other symptoms.