M08.921 ICD-10-CM Code: Juvenile arthritis, unspecified, right elbow
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FY 2026 Apr update / Diseases of the musculoskeletal system and connective tissue (M00-M99) / Inflammatory polyarthropathies (M05-M14)
M08.921
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceJuvenile arthritis, unspecified, right elbow
Juvenile arthritis of unspecified type affecting the right elbow in a child.
Buddy Insight
Juvenile arthritis, unspecified type, affecting the right elbow represents chronic inflammatory disease requiring ongoing pediatric rheumatology management with potential for significant functional impairment.
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
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Code Book Path
Inclusion Terms
OfficialICD-10-CM does not list inclusion terms for M08.921 in this effective period.
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for M08.921 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for M08.921 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for M08.921 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for M08.921 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for M08.921 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for M08.921 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 M08.921 an HCC code?
Yes. M08.921 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 M08.921
For M08.921to 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 M08.921 during that encounter, not just copy-forwarded from a problem list.
What This Code Means
M08.921 is the ICD-10-CM diagnosis code for juvenile arthritis, unspecified, right elbow. Juvenile arthritis of unspecified type affecting the right elbow in a child. M08.921 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, M08.921 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, M08.921 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.
The '1' in the final position indicates right side involvement; use M08.922 for left elbow. Because M08.921 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 M08.921 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •The '1' in the final position indicates right side involvement; use M08.922 for left elbow
- •Document the specific type of juvenile arthritis if known, as this code represents an unspecified type
Clinical Significance
Juvenile arthritis, unspecified type, affecting the right elbow represents chronic inflammatory disease requiring ongoing pediatric rheumatology management with potential for significant functional impairment. This diagnosis indicates need for specialized care and monitoring when specific arthritis subtype cannot be determined.
Documentation Requirements
- ✓Age at disease onset under 16 years documented
- ✓Clinical evidence of inflammatory arthritis specifically in right elbow
- ✓Documentation that specific juvenile arthritis type cannot be classified
- ✓Physical examination demonstrating right elbow joint inflammation
- ✓Laboratory studies consistent with inflammatory arthritis
- ✓Assessment of elbow function and range of motion
- ✓Current treatment regimen appropriate for juvenile arthritis
- ✓Monitoring plan for growth and developmental concerns