M08.439 ICD-10-CM Code: Pauciarticular juvenile rheumatoid arthritis, unspecified wrist
M08.439 maps to CMS-HCC V28 93 (RAF 0.617). Documentation must support MEAT. MEAT criteria · RAF calculator · HCC Buddy coding tools
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FY 2026 Apr update / Diseases of the musculoskeletal system and connective tissue (M00-M99) / Inflammatory polyarthropathies (M05-M14)
M08.439
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidancePauciarticular juvenile rheumatoid arthritis, unspecified wrist
A type of arthritis in children that affects only a few joints, involving the wrist when the specific side (left or right) is not documented or is bilateral.
Buddy Insight
This chronic autoimmune condition in children significantly impacts quality of life and requires long-term management with disease-modifying antirheumatic drugs (DMARDs) and biologics.
CMS-HCC V28
MappedHCC 93
RAF 0.617
CMS-HCC V24
MappedHCC 40
RAF 0.421
ACA/HHS
MappedHCC 56
Varies by metal level
ESRD/PACE
MappedHCC 40
RAF 0.058
RXHCC
MappedHCC 83
RAF 0.222
Code Book Path
Inclusion Terms
OfficialICD-10-CM does not list inclusion terms for M08.439 in this effective period.
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for M08.439 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for M08.439 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for M08.439 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for M08.439 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for M08.439 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for M08.439 in this effective period.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →
Is M08.439 an HCC code?
Yes. M08.439 (Pauciarticular juvenile rheumatoid arthritis, unspecified wrist) maps to Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders under the CMS-HCC V28 risk adjustment model (and Rheumatoid Arthritis and Inflammatory Connective Tissue Disease under V24), with a community non-dual aged RAF of 0.617. It is billable for payment year 2026.
Coder answer: M08.439 is billable and maps to V28 HCC 93, Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- M08.439
- Description
- Pauciarticular juvenile rheumatoid arthritis, unspecified wrist
- HCC (V28)
- HCC 93 — Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders
- RAF
- 0.617
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
Each model's RAF is its CMS base weight for that model's standard population, so weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. 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.
Work M08.439 in the Code Book — tabular path, V28 RAF, and MEAT checklist →
MEAT Criteria for M08.439
For M08.439 to 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 M08.439 during that encounter, not just copy-forwarded from a problem list.
Coder workflow notes
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What This Code Means
M08.439 is the ICD-10-CM diagnosis code for pauciarticular juvenile rheumatoid arthritis, unspecified wrist. A type of arthritis in children that affects only a few joints, involving the wrist when the specific side (left or right) is not documented or is bilateral. M08.439 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, M08.439 maps to Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders (HCC 93) with a community, non-dual, aged base RAF weight of 0.617. Under the older CMS-HCC V24 model, M08.439 maps to Rheumatoid Arthritis and Inflammatory Connective Tissue Disease (HCC 40) with a community, non-dual, aged base RAF weight of 0.421. 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.
Use this code when wrist involvement is documented but laterality is not specified in the record. Because M08.439 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 M08.439 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use this code when wrist involvement is documented but laterality is not specified in the record
- •Query the provider if possible to determine unilateral versus bilateral wrist involvement for more specific coding
Clinical Significance
This chronic autoimmune condition in children significantly impacts quality of life and requires long-term management with disease-modifying antirheumatic drugs (DMARDs) and biologics. Early diagnosis and treatment are crucial to prevent joint destruction and preserve function throughout the child's development.
Documentation Requirements
- ✓Age at onset (must be before 16 years old)
- ✓Number of joints affected (4 or fewer for pauciarticular)
- ✓Duration of symptoms (at least 6 weeks)
- ✓Evidence of joint inflammation (swelling, warmth, limited range of motion)
- ✓Exclusion of other arthritis types
- ✓Laboratory results if available (RF, ANA, anti-CCP)
- ✓Specific joint involvement documented
- ✓Response to anti-inflammatory medications
Commonly Confused Codes
- •M08.00: Unspecified juvenile rheumatoid arthritis when joint count is not documented
- •M08.1: Juvenile ankylosing spondylitis which affects spine primarily
- •M08.2: Juvenile rheumatoid arthritis with systemic onset (Still's disease)
- •M13.80: Other specified arthritis when patient is over 16 years old
- •M06.9: Adult rheumatoid arthritis when age at onset is unclear