M08.80 ICD-10-CM Code: Other juvenile arthritis, unspecified site
HCC Buddy Code Card
Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.
FY 2026 Apr update / Diseases of the musculoskeletal system and connective tissue (M00-M99) / Inflammatory polyarthropathies (M05-M14)
M08.80
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceOther juvenile arthritis, unspecified site
A form of childhood arthritis that does not fit into other specific categories, affecting an unspecified location in the body.
Buddy Insight
Other juvenile arthritis of unspecified site represents a broad category of pediatric inflammatory arthritis that doesn't fit into more specific juvenile arthritis classifications.
CMS-HCC V28
MappedHCC 93
RAF 0.175
CMS-HCC V24
MappedHCC 40
RAF 0.307
ACA/HHS
00
RAF 0
ESRD/PACE
MappedHCC 40
RAF 0.0
RXHCC
MappedHCC 83
RAF 0.0
Code Trumping
Basket needed
Code Book Path
Inclusion Terms
OfficialICD-10-CM does not list inclusion terms for M08.80 in this effective period.
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for M08.80 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for M08.80 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for M08.80 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for M08.80 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for M08.80 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for M08.80 in this effective period.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.
Is M08.80 an HCC code?
Yes. M08.80 maps to Rheumatoid Arthritis and Inflammatory Connective Tissue Disease under the CMS-HCC V28 risk adjustment model (and Rheumatoid Arthritis and Inflammatory Connective Tissue Disease under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
MEAT Criteria for M08.80
For M08.80to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed M08.80 during that encounter, not just copy-forwarded from a problem list.
What This Code Means
M08.80 is the ICD-10-CM diagnosis code for other juvenile arthritis, unspecified site. A form of childhood arthritis that does not fit into other specific categories, affecting an unspecified location in the body. M08.80 sits in the ICD-10-CM chapter for diseases of the musculoskeletal system and connective tissue (m00-m99), within the section covering inflammatory polyarthropathies (m05-m14).
Under the CMS-HCC V28 risk adjustment model, M08.80 maps to Rheumatoid Arthritis and Inflammatory Connective Tissue Disease (HCC 93) with a community, non-dual, aged base RAF weight of 0.175. Under the older V24 model, M08.80 mapped to the same category but with a base RAF weight of 0.307, V28 recalibrated weights across the entire model. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
This is a less specific code; attempt to identify the affected site and use more specific codes when possible. Because M08.80 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for M08.80 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This is a less specific code; attempt to identify the affected site and use more specific codes when possible
- •Use only when the site of arthritis cannot be determined from documentation
Clinical Significance
Other juvenile arthritis of unspecified site represents a broad category of pediatric inflammatory arthritis that doesn't fit into more specific juvenile arthritis classifications. This diagnosis indicates the presence of chronic inflammatory joint disease in children requiring specialized rheumatologic care to prevent long-term joint damage and functional impairment.
Documentation Requirements
- ✓Physician diagnosis of juvenile arthritis not fitting other specific categories
- ✓Documentation that site/location is unspecified or multiple unspecified joints
- ✓Evidence of inflammatory joint disease in pediatric patient
- ✓Age at onset documentation showing childhood presentation
- ✓Clinical findings consistent with inflammatory arthritis
- ✓Laboratory studies when available to support inflammatory process
- ✓Treatment plan addressing inflammatory arthritis management
- ✓Assessment of functional impact and disease activity
Commonly Confused Codes
- •M08.90: Juvenile arthritis unspecified versus other juvenile arthritis
- •M08.89: Other juvenile arthritis multiple sites versus unspecified site
- •M08.2: Juvenile arthritis with systemic onset versus other types
- •M13.9: Arthritis unspecified versus juvenile-specific arthritis
- •M08.4A: Pauciarticular JRA other specified site versus other juvenile arthritis