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v1.0.0
ICD-10 Guide
ICD-10 CodesM21.40

M21.40

Billable

Flat foot [pes planus] (acquired), unspecified foot

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

Code Description

ICD-10 M21.40 is a billable code used to indicate a diagnosis of flat foot [pes planus] (acquired), unspecified foot.

Key Diagnostic Point:

Acquired flat foot, or pes planus, is a condition characterized by the collapse of the arch of the foot, leading to a flat appearance. This condition can develop due to various factors, including injury, obesity, aging, or conditions such as diabetes or rheumatoid arthritis. Patients may experience symptoms such as pain in the foot, ankle, or lower leg, and may have difficulty with activities that require standing or walking for extended periods. The condition can lead to further complications, including misalignment of the knees and hips, which can result in additional musculoskeletal issues. Diagnosis typically involves a physical examination and may include imaging studies to assess the structure of the foot. Treatment options vary based on severity and may include orthotic devices, physical therapy, or surgical interventions to restore the arch and alleviate pain.

Code Complexity Analysis

Complexity Rating: Medium

Medium Complexity

Complexity Factors

  • Variability in clinical presentation and severity of symptoms
  • Differentiation from other foot deformities such as hallux valgus
  • Need for comprehensive documentation of acquired causes
  • Potential for co-morbid conditions affecting treatment and coding

Audit Risk Factors

  • Inadequate documentation of the acquired nature of the condition
  • Failure to specify the foot affected when applicable
  • Misclassification with congenital flat foot codes
  • Lack of supporting evidence for associated symptoms or treatments

Specialty Focus

Medical Specialties

Podiatry

Documentation Requirements

Detailed history of symptoms, physical examination findings, and treatment plans.

Common Clinical Scenarios

Patients presenting with foot pain, difficulty walking, or previous foot injuries.

Billing Considerations

Documentation should include any orthotic devices prescribed and their effectiveness.

Orthopedics

Documentation Requirements

Comprehensive assessment of foot structure, gait analysis, and imaging results.

Common Clinical Scenarios

Patients with flat foot seeking surgical intervention or conservative management.

Billing Considerations

Include details on any co-existing conditions that may affect treatment outcomes.

Coding Guidelines

Inclusion Criteria

Use M21.40 When
  • According to ICD
  • 10 guidelines, M21
  • 40 should be used when the flat foot is acquired and unspecified
  • Coders must ensure that the documentation supports the diagnosis and that it is not confused with congenital flat foot

Exclusion Criteria

Do NOT use M21.40 When
No specific exclusions found.

Related ICD-10 Codes

Related CPT Codes

28285CPT Code

Osteotomy, first metatarsal, with or without lengthening

Clinical Scenario

Used in surgical correction of flat foot deformities.

Documentation Requirements

Pre-operative assessment, surgical notes, and post-operative follow-up.

Specialty Considerations

Orthopedic surgeons must document the rationale for surgical intervention.

ICD-10 Impact

Diagnostic & Documentation Impact

Enhanced Specificity

ICD-10 Improvements

The transition to ICD-10 has allowed for more specific coding of flat foot conditions, improving the accuracy of diagnoses and treatment tracking. M21.40 provides a clear designation for acquired flat foot, facilitating better patient management.

ICD-9 vs ICD-10

The transition to ICD-10 has allowed for more specific coding of flat foot conditions, improving the accuracy of diagnoses and treatment tracking. M21.40 provides a clear designation for acquired flat foot, facilitating better patient management.

Reimbursement & Billing Impact

The transition to ICD-10 has allowed for more specific coding of flat foot conditions, improving the accuracy of diagnoses and treatment tracking. M21.40 provides a clear designation for acquired flat foot, facilitating better patient management.

Resources

Clinical References

  • •
    ICD-10-CM Official Guidelines for Coding and Reporting

Coding & Billing References

  • •
    ICD-10-CM Official Guidelines for Coding and Reporting

Frequently Asked Questions

What are the common causes of acquired flat foot?

Common causes include obesity, injury, aging, and conditions like diabetes and rheumatoid arthritis.

How is acquired flat foot diagnosed?

Diagnosis typically involves a physical examination, patient history, and imaging studies to assess foot structure.

What treatments are available for acquired flat foot?

Treatment options may include orthotic devices, physical therapy, and in some cases, surgical intervention.