What is ICD-10 code M08.279?

M08.279 is the ICD-10-CM diagnosis code for Juvenile rheumatoid arthritis with systemic onset, unspecified ankle and foot. A type of childhood arthritis with systemic symptoms affecting the ankle and foot when the specific side is not documented or is bilateral. M08.279 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. M08.279 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. M08.279 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. M08.279 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

What is the V28 vs V24 difference for M08.279?

CMS phased in the V28 risk adjustment model over payment years 2024 (33%), 2025 (67%), and 2026 (100%), replacing V24. V28 consolidates HCC categories, removes some lower-acuity conditions, and recalibrates RAF weights across the entire model. For M08.279, V28 maps to Rheumatoid Arthritis and Inflammatory Connective Tissue Disease at RAF 0.175 while V24 mapped to Rheumatoid Arthritis and Inflammatory Connective Tissue Disease at RAF 0.307. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting M08.279?

Use only when laterality is unspecified or bilateral involvement is documented Query provider documentation if a specific side can be determined for more precise coding Because M08.279 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score.

M08.279 ICD-10 Code: Juvenile rheumatoid arthritis

ICD-10-CM Code View

HCC Buddy Code Card

Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.

Code lookupM08.279Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the musculoskeletal system and connective tissue (M00-M99) / Inflammatory polyarthropathies (M05-M14)

M08.279

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Juvenile rheumatoid arthritis with systemic onset, unspecified ankle and foot

A type of childhood arthritis with systemic symptoms affecting the ankle and foot when the specific side is not documented or is bilateral.

Buddy Insight

Juvenile rheumatoid arthritis with systemic onset represents a severe form of childhood arthritis with significant systemic inflammation requiring intensive management.

CMS-HCC V28

Mapped

HCC 93

Rheumatoid Arthritis and Infl...

RAF 0.175

CMS-HCC V24

Mapped

HCC 40

Rheumatoid Arthritis and Infl...

RAF 0.307

ACA/HHS

Not risk-adjusted for this model/period.

RAF 0

ESRD/PACE

Mapped

HCC 40

Rheumatoid Arthritis and Infl...

RAF 0.0

RXHCC

Mapped

HCC 83

Rheumatoid Arthritis and Infl...

RAF 0.0

Code Trumping

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Code Book Path

Official

M08.2Juvenile rheumatoid arthritis with systemic onset

M08.27Juvenile rheumatoid arthritis with systemic onset, ankle and foot

M08.279Juvenile rheumatoid arthritis with systemic onset, unspecified ankle and foot

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for M08.279 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for M08.279 in this effective period.

Related Child Codes

Official

M08.271Juvenile rheumatoid arthritis with systemic onset, right ankle and foot

M08.272Juvenile rheumatoid arthritis with systemic onset, left ankle and foot

Includes

Official

ICD-10-CM does not list Includes notes for M08.279 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for M08.279 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for M08.279 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for M08.279 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for M08.279 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Patient age at onset (must be under 16 years)

Evidence of systemic symptoms (fever, rash, lymphadenopathy, hepatosplenomegaly)

Documentation of ankle and foot joint involvement without laterality specification or bilateral involvement

Laboratory evidence of systemic inflammation (elevated ESR, CRP)

MEAT Support

HCC Buddy guidance

Patient age at onset (must be under 16 years)

Evidence of systemic symptoms (fever, rash, lymphadenopathy, hepatosplenomegaly)

Documentation of ankle and foot joint involvement without laterality specification or bilateral involvement

Laboratory evidence of systemic inflammation (elevated ESR, CRP)

Audit Caution

HCC Buddy guidance

Using this code when laterality is clearly documented in the record

Failing to query physician for laterality when ankle/foot involvement is mentioned

Coding adult rheumatoid arthritis codes when patient had juvenile onset

Confusing unspecified ankle/foot with bilateral involvement

Common Mistakes

HCC Buddy guidance

M08.271 — Use when right ankle and foot specifically documented

M08.272 — Use when left ankle and foot specifically documented

M08.3 — Juvenile rheumatoid polyarthritis seronegative (affects multiple joints without systemic symptoms)

M25.579 — Pain in unspecified ankle and joints of unspecified foot (symptom code, not diagnostic)

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 M08.279 an HCC code?

Yes. M08.279 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

V28HCC 93, Rheumatoid Arthritis and Inflammatory Connective Tissue Disease

0.175

V24HCC 40, Rheumatoid Arthritis and Inflammatory Connective Tissue Disease

0.307

ESRDHCC 40, Rheumatoid Arthritis and Inflammatory Connective Tissue Disease

0.000

RxHCCHCC 83, Rheumatoid Arthritis and Inflammatory Connective Tissue Disease

0.000

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 M08.279

For M08.279to 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 M08.279 during that encounter, not just copy-forwarded from a problem list.

What This Code Means

M08.279 is the ICD-10-CM diagnosis code for juvenile rheumatoid arthritis with systemic onset, unspecified ankle and foot. A type of childhood arthritis with systemic symptoms affecting the ankle and foot when the specific side is not documented or is bilateral. M08.279 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, M08.279 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, M08.279 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.

Use only when laterality is unspecified or bilateral involvement is documented. Because M08.279 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 M08.279 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Use only when laterality is unspecified or bilateral involvement is documented
•Query provider documentation if a specific side can be determined for more precise coding

Clinical Significance

Juvenile rheumatoid arthritis with systemic onset represents a severe form of childhood arthritis with significant systemic inflammation requiring intensive management. Ankle and foot involvement can significantly impact mobility, growth, and development, requiring comprehensive orthopedic and rheumatologic care with potential for long-term disability.

Documentation Requirements

✓Patient age at onset (must be under 16 years)
✓Evidence of systemic symptoms (fever, rash, lymphadenopathy, hepatosplenomegaly)
✓Documentation of ankle and foot joint involvement without laterality specification or bilateral involvement
✓Laboratory evidence of systemic inflammation (elevated ESR, CRP)
✓Exclusion of other causes of arthritis and systemic illness
✓Duration of symptoms (minimum 6 weeks for JRA diagnosis)
✓Physical examination findings of ankle/foot swelling, warmth, or limited motion
✓Assessment of functional impact including gait and weight-bearing capacity

Commonly Confused Codes

•M08.271: Use when right ankle and foot specifically documented
•M08.272: Use when left ankle and foot specifically documented
•M08.3: Juvenile rheumatoid polyarthritis seronegative (affects multiple joints without systemic symptoms)
•M25.579: Pain in unspecified ankle and joints of unspecified foot (symptom code, not diagnostic)
•M79.3: Panniculitis, unspecified (may be confused due to systemic symptoms)