Mallet finger describes an injury to the tip of a finger or thumb that stops it from being able to straighten properly. People sometimes refer to mallet finger as “baseball finger,” as it is a fairly common sporting injury among ball players.

A person wearing a splint on their finger to treat mallet finger.Share on Pinterest
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Mallet finger occurs when something forces the tip of a finger or thumb to bend further than usual. Although it is often the result of a sporting injury, it can happen during normal daily activities, such as tucking in sheets.

This article explains what mallet finger is and what causes it. It also explains how to treat it immediately with first aid and what to expect from ongoing treatment.

When something hard, such as a ball, hits the top of a finger or thumb, it can make the digit bend further than it usually does. If this damages the tendons, a person may not be able to straighten the affected digit.

A 2022 article notes that each finger has three bones, called phalanges, and each thumb has two. Tendons connect these bones to the muscles in the forearm.

Extensor tendons attach near the top of each digit on the back of the hand. These straighten the fingers and thumbs. Flexor tendons attach to the digits on the palm side, and bend the fingers.

Sometimes, an object hits the tip of a finger or thumb with enough force to stretch or tear the extensor tendon, making the top of the digit droop. This is called mallet finger.

Occasionally, the force of the impact pulls a piece of bone away with the torn tendon. This is called an avulsion fracture.

The most obvious symptom is that the tip of the finger or thumb droops. A person will only be able to straighten it if they push it up with their other hand or press it against another surface.

Most people with mallet finger experience the following at the injury site:

  • sharp pain
  • swelling
  • bruising

The American Society for Surgery of the Hand (ASSH) adds that blood sometimes collects under the damaged finger’s nail. The nail may become discolored and begin to detach.

The American Academy of Orthopaedic Surgeons (AAOS) recommends applying an ice pack immediately after sustaining the injury, or as soon as possible. It also advises people to elevate the hand above the heart, with the fingers pointing upward.

People can also take anti-inflammatory pain relievers, such as ibuprofen or naproxen.

If the person is wearing any jewelry on the injured finger or thumb, they should remove it in case of swelling.

The ASSH states that people should see a doctor within the first few days of the injury. Without treatment, the finger may not heal and function as it should, which can result in pain.

It is also particularly important that children receive prompt treatment. Children’s bones are still growing, and damage to the growing part of a bone can lead to permanent deformities.

People should seek immediate medical attention if there is blood underneath the nail or the nail is becoming detached.

The AAOS notes that this can indicate a wound in the nail bed or an open fracture, either of which can increase the risk of infection.

After examining the person’s finger for cuts or bleeding, doctors usually recommend an X-ray to check for broken bones or dislocated joints.

According to the AAOS, most doctors recommend a splint when treating mallet finger. The splint keeps the finger or thumb straight while the injury heals.

People usually need to wear the splint for 8 weeks. They will need to wear the splint all of the time, including when they bathe.

If the finger is healing well after this time, doctors may reduce the amount of time the person wears the splint. However, they usually recommend wearing it during sleep for at least another 3–4 weeks.

If the finger joints are out of alignment and a large fragment of bone has broken off, doctors may recommend surgery. The ASSH explains that surgeons can use wire or tiny screws to hold the bones in place. Alternatively, they may be able to stitch the ends of the tendon together.

Wearing a splint can make bathing difficult, but it is important to keep the area clean and dry. The AAOS recommends wrapping two layers of plastic around the finger before washing.

After bathing or showering, a person may need to change their splint, or wash and dry it, before putting it back on. It is important to keep the injured finger straight during this time, as any drooping of the finger can interrupt the healing process.

Sometimes, wearing a splint can irritate the skin. People with mallet finger need to keep an eye out for any skin problems.

Doctors may also recommend exercises to restore movement to the injured finger.

Below, we answer some questions that people often ask about mallet finger.

Is it a sign of arthritis?

Mallet finger is not a sign of arthritis. Although the symptoms overlap, with both conditions causing swelling, pain, and restricted movement, mallet finger is an injury rather than a permanent change to the joint.

Can it cause arthritis?

Sometimes, if the mallet finger injury damages a joint, a person may develop post-traumatic arthritis. Most people recover fully from this within 2–3 months.

The Arthritis Foundation says that people who have injured their joints are more likely to develop osteoarthritis, even if the joint has healed properly.

It adds that fractures and dislocated joints are among the most common injuries that lead to arthritis.

Mallet finger refers to an injury that stops a person from straightening their finger or thumb. Typically, the top part of the digit droops. This occurs because the tendon that connects the muscles and bones becomes overstretched or torn.

People should seek medical treatment within the first few days of the injury. It is particularly important that children receive prompt treatment to help avoid permanent deformities. It is also best to see a doctor if there is blood under the nail bed.

People with mallet finger may need a splint to keep their finger or thumb straight while it recovers. Some people may need surgery, especially if the tendon pulls off part of the bone as it tears.