ICD-10 Code M18.1: Unilateral primary osteoarthritis of first carpometacarpal joint
M18.1 is an ICD-10 diagnosis entry used to group records related to Unilateral primary osteoarthritis of first carpometacarpal joint. 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. 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).
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).
When is it used?
- May be used when a clinician documents unilateral primary osteoarthritis of first carpometacarpal joint 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.
Code hierarchy
Official coding notes
- Primary osteoarthritis of first carpometacarpal joint NOS
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
Related codes
Sibling codes
Coding guidelines
Compatibility
Common synonyms
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.