ICD10
ICD-10 Code M23.21: Derangement of anterior horn of medial meniscus due to old tear or injury
Reviewed by HealthAssure Clinical TeamUpdated 26 May 2026
What is this code?
ICD-10 entries help standardize how diagnoses are organized for coding, reporting, analytics, and documentation. This code sits within the broader ICD-10 area for Diseases of the musculoskeletal system and connective tissue (M00-M99).
đź“‹Clinical overview
This ICD-10 code is commonly used when documentation describes derangement of a knee meniscus due to old tear or injury. The most accurate code depends on whether the meniscus is medial, lateral, or unspecified, which horn or part is involved, and which knee is affected.
When is it used?
- May be used when a clinician documents derangement of anterior horn of medial meniscus due to old tear or injury in a patient's medical record.
- May appear in hospital records, claims, referrals, and clinical documentation.
- This code may act more like a grouping or parent code, so a more specific child code may be used in final documentation when available.
What it does not mean
- A code alone does not explain severity, treatment plan, or outcome.
- A medical code should not be treated as a substitute for a doctor's diagnosis or advice.
- This entry may represent a broader category rather than the most specific billable code.
đź©şClinical context
When commonly used
- Orthopedic, sports-medicine, rehabilitation, and imaging workflows where chronic or old-tear meniscal derangement is part of the documented knee problem list.
- Coding and utilization-review workflows where the record supports meniscal derangement due to old tear or injury and the final code changes based on compartment, horn location, or laterality.
Common management context
- Evaluation often includes knee pain and mechanical-symptom review, physical examination, MRI or other imaging context, and planning for orthopedic follow-up or rehabilitation.
- Documentation usually becomes more specific when the chart identifies medial versus lateral meniscus, anterior versus posterior horn, other-part involvement, or right versus left knee.
- Specialist context already linked on this page includes Orthopedic Specialist, Rheumatologist, ENT Specialist.
🔍Key distinctions
Important notes
- These ICD-10 codes are reserved for chronic or old-tear-or-injury meniscal derangement rather than acute traumatic meniscal injury.
- Meniscal compartment, horn location, and laterality all affect final code specificity inside this family.
- Medial-meniscus derangement is coded separately from lateral-meniscus derangement when the chart identifies the involved compartment more specifically.
- Anterior-horn meniscal derangement is coded separately from posterior-horn, other-part, or unspecified meniscal derangement.
- Documentation that describes meniscal derangement due to old tear or injury is coded differently from acute traumatic meniscal injury, ligament derangement, or other knee disorders.
Related codes to consider
M23.211Derangement of anterior horn of medial meniscus due to old tear or injury, right knee
Related meniscal-derangement ICD-10 code; documentation often becomes more specific when the chart identifies medial versus lateral compartment, horn location, laterality, or acute-versus-old injury context.
M23.212Derangement of anterior horn of medial meniscus due to old tear or injury, left knee
Related meniscal-derangement ICD-10 code; documentation often becomes more specific when the chart identifies medial versus lateral compartment, horn location, laterality, or acute-versus-old injury context.
M23.219Derangement of anterior horn of medial meniscus due to old tear or injury, unspecified knee
Related meniscal-derangement ICD-10 code; documentation often becomes more specific when the chart identifies medial versus lateral compartment, horn location, laterality, or acute-versus-old injury context.
Code hierarchy
chapter
13Diseases of the musculoskeletal system and connective tissue (M00-M99)
block
M00-M25Arthropathies
block
M20-M25Other joint disorders
category
M23Internal derangement of knee
category
M23.2Derangement of meniscus due to old tear or injury
currentM23.2
Where you may see this code
You may see this entry in coding references, medical records, or claims workflows when a broader diagnosis category is being reviewed before a more specific code is chosen.
Related specialists
Orthopedic SpecialistRheumatologistENT Specialist
Related codes
Sibling codes
M23.20Derangement of unspecified meniscus due to old tear or injuryM23.22Derangement of posterior horn of medial meniscus due to old tear or injuryM23.23Derangement of other medial meniscus due to old tear or injuryM23.24Derangement of anterior horn of lateral meniscus due to old tear or injuryM23.25Derangement of posterior horn of lateral meniscus due to old tear or injuryM23.26Derangement of other lateral meniscus due to old tear or injury
Mapped diagnoses and classifications
Coding guidelines
Compatibility
Legacy code aligns to an official FY 2026 category. Frontend should resolve to the official category page and surface the billable child codes.
Legacy codes
M23.21
Replacement codes
M23.211 — Derangement of anterior horn of medial meniscus due to old tear or injury, right kneeM23.212 — Derangement of anterior horn of medial meniscus due to old tear or injury, left kneeM23.219 — Derangement of anterior horn of medial meniscus due to old tear or injury, unspecified knee
Common synonyms
Derangement of anterior horn of medial meniscus due to old tear or injury
Frequently asked questions
About this content
This page is prepared by HealthAssure's clinical team using official coding standards from ICD-10. AI tools assist with drafting explanations, which are then reviewed and verified by healthcare professionals for accuracy. This content is for informational purposes and does not replace professional medical advice. Meet our team.