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v1.0.0
ICD-10 Guide
ICD-10 CodesM21.42

M21.42

Billable

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

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

Code Description

ICD-10 M21.42 is a billable code used to indicate a diagnosis of flat foot [pes planus] (acquired), left foot.

Key Diagnostic Point:

Acquired flat foot, or pes planus, is a condition characterized by the collapse of the medial longitudinal 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. In adults, acquired flat foot often results from dysfunction of the posterior tibial tendon, which plays a crucial role in maintaining the arch. Symptoms may include pain in the foot, ankle, or lower leg, difficulty walking, and fatigue. Diagnosis typically involves a physical examination, patient history, and imaging studies such as X-rays or MRI to assess the structure of the foot and rule out other conditions. Treatment options vary based on severity and may include orthotic devices, physical therapy, medications for pain relief, and in some cases, surgical intervention to correct the deformity and restore function.

Code Complexity Analysis

Complexity Rating: Medium

Medium Complexity

Complexity Factors

  • Differentiating between acquired and congenital flat foot
  • Identifying the specific foot affected (left vs. right)
  • Understanding associated conditions that may complicate coding
  • Documentation requirements for surgical vs. non-surgical treatment

Audit Risk Factors

  • Inadequate documentation of the condition's acquired nature
  • Failure to specify the affected foot
  • Lack of supporting evidence for associated treatments
  • Misuse of codes for congenital vs. acquired conditions

Specialty Focus

Medical Specialties

Podiatry

Documentation Requirements

Detailed patient history, physical examination findings, imaging results, and treatment plans.

Common Clinical Scenarios

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

Billing Considerations

Ensure clear documentation of the acquired nature and any associated conditions.

Orthopedics

Documentation Requirements

Comprehensive assessment of foot structure, functional limitations, and treatment options.

Common Clinical Scenarios

Patients with flat foot requiring surgical intervention or conservative management.

Billing Considerations

Document any surgical procedures performed and their relation to the flat foot condition.

Coding Guidelines

Inclusion Criteria

Use M21.42 When
  • Follow the ICD
  • CM guidelines for coding acquired conditions
  • Ensure accurate documentation of the condition's acquired nature and specify the affected foot
  • Include any relevant comorbidities that may impact treatment

Exclusion Criteria

Do NOT use M21.42 When
No specific exclusions found.

Related ICD-10 Codes

Related CPT Codes

28285CPT Code

Correction of flat foot

Clinical Scenario

Used when surgical intervention is required for severe acquired flat foot.

Documentation Requirements

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

Specialty Considerations

Orthopedic surgeons must document the rationale for surgery and expected outcomes.

ICD-10 Impact

Diagnostic & Documentation Impact

Enhanced Specificity

ICD-10 Improvements

The transition to ICD-10 has allowed for more specific coding of conditions like acquired flat foot, improving the accuracy of patient records and treatment plans. This specificity aids in better tracking of treatment outcomes and resource allocation.

ICD-9 vs ICD-10

The transition to ICD-10 has allowed for more specific coding of conditions like acquired flat foot, improving the accuracy of patient records and treatment plans. This specificity aids in better tracking of treatment outcomes and resource allocation.

Reimbursement & Billing Impact

The transition to ICD-10 has allowed for more specific coding of conditions like acquired flat foot, improving the accuracy of patient records and treatment plans. This specificity aids in better tracking of treatment outcomes and resource allocation.

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 is the difference between acquired and congenital flat foot?

Acquired flat foot develops due to factors such as injury or disease, while congenital flat foot is present at birth and is due to developmental issues.