M20.01 Mallet finger

Name of the Condition

• Mallet finger
• ICD-10-CM Code: M20.01

Summary

Mallet finger is a condition characterized by the inability to extend the distal interphalangeal (DIP) joint of a finger due to injury or damage to the extensor tendon. This results in a drooping appearance of the fingertip and can affect function, particularly in gripping or manipulating objects.

Causes

Mallet finger typically occurs when the extensor tendon at the DIP joint is torn or stretched, often from a sudden forceful flexion injury. Common mechanisms include a direct blow to the fingertip or a laceration that severs the tendon. In some cases, the injury may involve a small avulsion fracture of the bone where the tendon attaches.

Risk Factors

• Participation in sports or activities with high risk of finger trauma (e.g., basketball, volleyball)
• Occupational tasks requiring repetitive or forceful finger use
• History of prior finger injuries or tendon damage
• Age-related tendon degeneration, which may increase susceptibility to injury

Symptoms

• Inability to actively straighten the fingertip at the DIP joint
• Visible drooping of the fingertip when attempting to extend the finger
• Pain, swelling, or tenderness over the DIP joint
• Bruising or discoloration around the injured area
• Reduced grip strength or difficulty performing fine motor tasks

Diagnosis

Diagnosis is based on clinical evaluation, including assessment of finger extension and tenderness at the DIP joint. Imaging, such as X-rays, may be used to identify associated fractures or tendon avulsions. Patient history of trauma or injury to the fingertip is critical for confirming the diagnosis.

Treatment Options

• Immobilization of the DIP joint in extension using a splint or brace for 6–8 weeks to allow tendon healing
• Nonsteroidal anti-inflammatory drugs (NSAIDs) for pain and swelling
• Physical therapy to restore range of motion and strength after immobilization
• Surgical repair may be considered for severe tendon tears or displaced fractures

Prognosis and Follow-Up

Most cases of mallet finger heal with conservative treatment, though full recovery may take several months. Follow-up appointments are necessary to monitor healing and adjust immobilization as needed. Persistent stiffness or incomplete extension may require additional therapy or intervention.

Complications

• Chronic stiffness or limited range of motion in the DIP joint
• Re-rupture of the tendon if immobilization is discontinued prematurely
• Development of a swan neck deformity (hyperextension at the proximal interphalangeal joint) in untreated cases
• Persistent pain or functional impairment if healing is incomplete

Lifestyle & Prevention

• Use protective gear (e.g., padded gloves) during high-risk activities to reduce injury risk
• Avoid forceful flexion of the fingertip after injury until fully healed
• Perform gentle range-of-motion exercises as directed to maintain joint flexibility
• Seek prompt treatment for finger injuries to prevent complications

When to Seek Professional Help

• Inability to extend the fingertip after a finger injury
• Severe pain, swelling, or deformity of the finger
• Signs of infection (e.g., redness, warmth, pus) at the injury site
• Lack of improvement after initial home care or immobilization

Tips for Medical Coders

• Code M20.01 is specific to mallet finger and should be used when the condition is documented. Ensure the medical record supports the diagnosis, including details of the injury mechanism or physical findings. Documentation should clarify whether the injury is acute or chronic to guide appropriate coding. Avoid using this code for unspecified finger deformities or other tendon injuries without clear clinical correlation.