Mallet Finger:
When the Fingertip Won't Straighten

What is a mallet finger?

Each finger is straightened by a thin, flat extensor tendon running along its back. Its final part attaches to the base of the last finger bone (the distal phalanx), and it is the only structure that actively straightens the last joint — the distal interphalangeal (DIP) joint. If that end of the tendon is stretched, torn, or pulls off a small piece of bone, the fingertip can no longer be lifted actively. It hangs in a bent position, a bit like the head of a mallet; the injury is also called "drop finger" or "baseball finger". In Japanese it is tsuchi-yubi (槌指) or mallet finger (マレット指).

There are two main types:

Tendinous mallet finger — the tendon itself is torn or stretched, with no fracture on X-ray.
Bony mallet finger (mallet fracture) — the tendon pulls off a fragment of bone from the back of the distal phalanx. The size of the fragment, and whether the joint has slipped out of line (subluxation), strongly influence treatment.

Who gets it and how

In a five-year study of all adults treated for musculoskeletal trauma in Edinburgh, mallet finger occurred at about 9.9 per 100,000 people per year. Unlike many sports injuries, it was most common in middle age, and, like most soft-tissue injuries in that study, more frequent in men (Clayton and Court-Brown, Injury, 2008).

The typical mechanism is a sudden force that bends the fingertip while the tendon is trying to hold it straight — a ball striking the tip in volleyball, basketball, baseball or softball, or a fall onto an outstretched finger. In older adults, the tendon can give way with surprisingly little force, such as tucking in a bed sheet or pulling on a sock. A cut across the back of the last joint (for example in the kitchen) can also divide the tendon; that is an open injury and is managed differently.

Symptoms and warning signs

The fingertip rests in a bent position and cannot be straightened by its own muscles, although it can usually be pushed straight with the other hand. There may be pain, swelling and bruising over the back of the last joint, but some tendinous injuries are almost painless, which is one reason people delay. If the droop is left untreated for a long time, some people develop a swan-neck deformity, where the middle joint over-straightens while the tip stays bent.

Diagnosis

The diagnosis is usually clear from the appearance: the doctor checks whether the fingertip can be straightened actively and whether the middle joint is affected. X-rays, especially a true side view of the finger, are essential. They show whether there is a fracture, how much of the joint surface the fragment involves, and whether the distal phalanx has slipped towards the palm side. Ultrasound or MRI is rarely needed. Because a fracture or joint subluxation can change the treatment plan, it is better to have an X-ray than to assume a mallet finger is "just a sprain".

Treatment options

Treatment depends on the type of injury, the size of any bone fragment, joint alignment, how long ago it happened, and practical factors such as work and the ability to keep a splint on. The overview below is simplified.

Situation	Usual first approach	Notes
Tendinous (no fracture)	Continuous splinting	Commonly about 6–8 weeks full time, then gradual weaning
Small bone fragment, joint aligned	Continuous splinting	Repeat X-rays may be used to check alignment
Large fragment or joint subluxation	Surgery is often discussed	Aim is to restore joint alignment
Open injury (cut tendon)	Urgent wound care	The tendon is often repaired at the same time
Late presentation	Splinting is still often tried	Surgery may be considered for persistent problems

Splinting

The core of non-surgical treatment is a small splint that holds only the last joint straight (or very slightly over-straightened), leaving the middle joint free to move. It can be a prefabricated plastic "Stack" splint, a padded aluminium splint, a custom-moulded thermoplastic splint made by a hand therapist, or sometimes a small finger cast. The splint is typically worn day and night for about 6–8 weeks, followed by a period of gradual weaning and, in many protocols, night-time splinting.

The most important rule is that the fingertip must not be allowed to bend during the full-time phase — even briefly when washing or changing the splint. Clinicians commonly teach patients to keep the fingertip supported flat on a table while the splint is off for skin care. Many protocols restart the full-time period if the tip is allowed to drop. Skin irritation and pressure under the splint are common, so checking the skin and adjusting the fit matters.

A small residual droop after treatment is common and often causes little trouble. In a randomised trial of 51 patients, adding a month of night splinting after the full-time period did not improve the result; the average remaining lag was about 14 degrees, and about one-third had 20 degrees or more, with little effect on reported disability (Gruber et al., Hand, 2014). Delays in starting treatment do not necessarily rule out splinting: in an older comparison, splinting begun more than four weeks after injury restored good extension about as often as splinting begun within two weeks (Garberman et al., Journal of Hand Surgery American Volume, 1994).

Surgery

Surgery is mainly considered for bony mallet injuries with a large fragment or when the joint has slipped out of alignment, for open injuries, and occasionally for people who cannot practically wear a splint continuously. Common techniques include fixing the joint with thin wires, often using an extension-block pinning method in which one wire acts as a buttress to push the fragment back into place, as well as small screws, hook plates or suture anchors. Surgical risks include infection around the wires, nail deformity, stiffness and wire problems.

Typical mallet finger	Splinting	Surgery
Main use	Most tendinous and many bony injuries	Selected bony injuries, especially with subluxation; open injuries
Daily demands	Splint must stay on continuously for weeks	Wires or implants for several weeks; wound care
Main downsides	Skin irritation; failure if the tip is allowed to bend; small residual droop common	Infection, nail problems, stiffness, implant issues
Average result	Broadly similar in the available studies, which are mostly small and of mixed quality

Recovery

After the full-time splinting period, most protocols gradually reduce splint use over several weeks while gentle bending exercises are introduced, often guided by a hand therapist. Forceful gripping and ball sports with the affected finger are usually resumed only after this weaning period; some athletes can return earlier with the finger protected. A mild bump over the back of the joint and some stiffness can persist for months. Full recovery commonly takes around three months or more, and it is normal for the result to keep improving slowly after the splint comes off.

The Cochrane review on this topic noted that the trials available were small and methodologically limited, so many details of splinting protocols — such as exact durations and weaning schedules — still rest on clinical experience rather than strong evidence (Handoll and Vaghela, Cochrane Database of Systematic Reviews, 2004). Your treating clinic's instructions should take priority.

When to see a doctor

If the tip of a finger droops after a jammed finger or a minor knock and you cannot straighten it yourself, it is worth visiting an orthopaedic clinic (整形外科) for an X-ray rather than waiting to see whether it improves. Until then, keeping the fingertip straight with a simple splint or tape and avoiding bending it is a sensible first step. A cut over the back of the last finger joint should be seen the same day. Ask whether there is a fracture, whether the joint is aligned, how long the splint is needed, and whether a hand therapist or hand surgeon should be involved.