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ICD-10 Guide
ICD-10 CodesM21.4

M21.4

Billable

Flat foot [pes planus] (acquired)

BILLABLE STATUSYes
IMPLEMENTATION DATEOctober 1, 2015
LAST UPDATED09/17/2025

Code Description

ICD-10 M21.4 is a billable code used to indicate a diagnosis of flat foot [pes planus] (acquired).

Key Diagnostic Point:

Acquired flat foot, or pes planus, is a condition characterized by the collapse of the medial longitudinal arch of the foot, resulting in a flat appearance. This deformity can arise due to various factors including trauma, obesity, aging, or conditions such as rheumatoid arthritis or diabetes. Unlike congenital flat foot, which is present at birth, acquired flat foot develops over time and can lead to pain and dysfunction in the foot and ankle. Patients may experience symptoms such as foot fatigue, pain in the arch or heel, and difficulty with activities that require standing or walking for prolonged periods. The condition can also lead to secondary issues such as hallux valgus, where the big toe deviates laterally, and other toe abnormalities. Treatment options may include orthotic devices, physical therapy, and in some cases, surgical interventions to correct the deformity and alleviate symptoms. Proper diagnosis and management are essential to prevent further complications and improve the patient's quality of life.

Code Complexity Analysis

Complexity Rating: Medium

Medium Complexity

Complexity Factors

  • Differentiating between congenital and acquired flat foot
  • Identifying associated conditions such as hallux valgus
  • Understanding the impact of comorbidities like obesity and diabetes
  • Documenting the severity and functional limitations of the condition

Audit Risk Factors

  • Inadequate documentation of the acquired nature of the condition
  • Failure to document associated conditions like hallux valgus
  • Lack of clarity on the functional limitations caused by the flat foot
  • Improper coding of treatment procedures related to the condition

Specialty Focus

Medical Specialties

Podiatry

Documentation Requirements

Detailed foot examination findings, including arch assessment and any associated deformities.

Common Clinical Scenarios

Patients presenting with foot pain, difficulty walking, or deformities such as bunions.

Billing Considerations

Ensure to document the specific type of flat foot and any corrective measures taken.

Orthopedics

Documentation Requirements

Comprehensive assessment of foot mechanics and any imaging studies performed.

Common Clinical Scenarios

Patients with flat foot requiring surgical intervention or those with associated joint pain.

Billing Considerations

Document the rationale for surgical procedures and any pre-operative assessments.

Coding Guidelines

Inclusion Criteria

Use M21.4 When
  • Follow official coding guidelines for M21
  • 4, ensuring accurate documentation of the acquired nature of the flat foot
  • Include any associated conditions and specify the treatment plan

Exclusion Criteria

Do NOT use M21.4 When
  • Exclude congenital flat foot codes unless there is a clear distinction

Related ICD-10 Codes

Related CPT Codes

28296CPT Code

Osteotomy, first metatarsal

Clinical Scenario

Used in surgical correction of hallux valgus associated with flat foot.

Documentation Requirements

Document the indication for surgery and pre-operative assessments.

Specialty Considerations

Podiatrists and orthopedic surgeons should ensure clear documentation of the surgical approach.

ICD-10 Impact

Diagnostic & Documentation Impact

Enhanced Specificity

ICD-10 Improvements

The transition to ICD-10 has allowed for more specific coding of acquired flat foot, improving the ability to capture the complexity of the condition and its associated treatments.

ICD-9 vs ICD-10

The transition to ICD-10 has allowed for more specific coding of acquired flat foot, improving the ability to capture the complexity of the condition and its associated treatments.

Reimbursement & Billing Impact

The transition to ICD-10 has allowed for more specific coding of acquired flat foot, improving the ability to capture the complexity of the condition and its associated treatments.

Resources

Clinical References

  • •
    American Academy of Orthopaedic Surgeons

Coding & Billing References

  • •
    American Academy of Orthopaedic Surgeons

Frequently Asked Questions

What are the common causes of acquired flat foot?

Common causes include obesity, trauma, aging, and conditions such as rheumatoid arthritis and diabetes.

How can acquired flat foot be treated?

Treatment options include orthotics, physical therapy, and surgical interventions depending on the severity and associated conditions.