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M06.4 ICD-10-CM Code: Inflammatory polyarthropathy

M06.4 maps to CMS-HCC V28 94 (RAF 0.268). Documentation must support MEAT. MEAT criteria · RAF calculator · HCC coding software

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

M06.4

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

Inflammatory polyarthropathy

Inflammation affecting multiple joints that is related to rheumatoid arthritis or similar inflammatory conditions, but does not meet criteria for classic rheumatoid arthritis.

Buddy the Bee presenting code insight

Buddy Insight

Inflammatory polyarthropathy represents a serious chronic condition involving multiple joints with ongoing inflammation that may lead to joint destruction and functional disability.

CMS-HCC V28

HCC 94

RAF 0.268

CMS-HCC V24

HCC 40

RAF 0.421

ACA/HHS

HCC 57

Varies by metal level

ESRD/PACE

HCC 40

RAF 0.058

RXHCC

HCC 83

RAF 0.222

Code Book Path

Official
M06Other rheumatoid arthritis
M06.4Inflammatory polyarthropathy

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for M06.4 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for M06.4 in this effective period.

Related Child Codes

Official
M06.0Rheumatoid arthritis without rheumatoid factor
M06.1Adult-onset Still's disease
M06.2Rheumatoid bursitis
M06.3Rheumatoid nodule
M06.8Other specified rheumatoid arthritis

Includes

Official

ICD-10-CM does not list Includes notes for M06.4 in this effective period.

Excludes 1

Official
  • polyarthritis NOS (M13.0)

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for M06.4 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for M06.4 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for M06.4 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance
Documentation of inflammation affecting multiple joints simultaneously
Clinical evidence of polyarticular involvement (≥5 joints typically)
Inflammatory markers supporting active disease (ESR, CRP elevation)
Assessment of joint function and range of motion limitations

MEAT Support

HCC Buddy guidance
Documentation of inflammation affecting multiple joints simultaneously
Clinical evidence of polyarticular involvement (≥5 joints typically)
Inflammatory markers supporting active disease (ESR, CRP elevation)
Assessment of joint function and range of motion limitations

Audit Caution

HCC Buddy guidance
Using this code when patient meets criteria for specific rheumatoid arthritis diagnosis
Coding single joint inflammation instead of recognizing polyarticular pattern
Missing inflammatory markers that would support the diagnosis
Failing to document multiple joint involvement adequately

Common Mistakes

HCC Buddy guidance
M05.9 — Rheumatoid arthritis with rheumatoid factor, unspecified (when RF positive)
M06.9 — Rheumatoid arthritis, unspecified (when meets RA criteria)
M79.3 — Panniculitis, unspecified (localized inflammation without joint involvement)
M25.50 — Pain in unspecified joint (symptom without inflammatory evidence)

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 M06.4 an HCC code?

Yes. M06.4 (Inflammatory polyarthropathy) maps to Systemic Lupus Erythematosus and Other Specified Systemic Connective Tissue 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 0.268. It is billable for payment year 2026.

Coder answer: M06.4 is billable and maps to V28 HCC 94, Systemic Lupus Erythematosus and Other Specified Systemic Connective Tissue Disorders. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code
M06.4
Description
Inflammatory polyarthropathy
HCC (V28)
HCC 94 — Systemic Lupus Erythematosus and Other Specified Systemic Connective Tissue Disorders
RAF
0.268
Billable
Yes
Payment year
2026

HCC Category Mapping

V28HCC 94, Systemic Lupus Erythematosus and Other Specified Systemic Connective Tissue Disorders
0.268
V24HCC 40, Rheumatoid Arthritis and Inflammatory Connective Tissue Disease
0.421
ESRDHCC 40, Rheumatoid Arthritis and Inflammatory Connective Tissue Disease
0.058
RxHCCHCC 83, Rheumatoid Arthritis and Inflammatory Connective Tissue Disease
0.222

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 M06.4 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for M06.4

For M06.4 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 M06.4 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

M06.4 is the ICD-10-CM diagnosis code for inflammatory polyarthropathy. Inflammation affecting multiple joints that is related to rheumatoid arthritis or similar inflammatory conditions, but does not meet criteria for classic rheumatoid arthritis. M06.4 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, M06.4 maps to Systemic Lupus Erythematosus and Other Specified Systemic Connective Tissue Disorders (HCC 94) with a community, non-dual, aged base RAF weight of 0.268. Under the older CMS-HCC V24 model, M06.4 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 M06.4 when the provider wording supports inflammatory polyarthropathy. Check the FY2026 tabular notes and the full code path before the final code choice. Because M06.4 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 M06.4 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •Use M06.4 when the provider wording supports inflammatory polyarthropathy. Check the FY2026 tabular notes and the full code path before the final code choice.
  • •For this DOS, capture the provider's current assessment and the care action documented for inflammatory polyarthropathy. Keep the checklist tied to the note.
  • •Do not swap M06.4 with M06.0. The FY2026 tabular describes M06.0 as rheumatoid arthritis without rheumatoid factor. Follow the documented detail.
  • •M06.4 maps to V28 HCC 94, Systemic Lupus Erythematosus and Other Specified Systemic Connective Tissue Disorders. The mapping does not replace the documentation review. The code still has to match the note.
  • •Ask Buddy to show the official notes for M06.4 or compare its code path with M06.0.

Clinical Significance

Inflammatory polyarthropathy represents a serious chronic condition involving multiple joints with ongoing inflammation that may lead to joint destruction and functional disability. This diagnosis indicates need for aggressive anti-inflammatory treatment and regular monitoring for disease progression.

Documentation Requirements

  • ✓Documentation of inflammation affecting multiple joints simultaneously
  • ✓Clinical evidence of polyarticular involvement (≥5 joints typically)
  • ✓Inflammatory markers supporting active disease (ESR, CRP elevation)
  • ✓Assessment of joint function and range of motion limitations
  • ✓Exclusion of other specific inflammatory arthropathies when possible
  • ✓Response to anti-inflammatory treatments documented
  • ✓Functional assessment and impact on activities of daily living
  • ✓Monitoring plan for disease progression and complications

Excludes 1, Do NOT code together

  • polyarthritis NOS (M13.0)

Commonly Confused Codes

  • •M05.9: Rheumatoid arthritis with rheumatoid factor, unspecified (when RF positive)
  • •M06.9: Rheumatoid arthritis, unspecified (when meets RA criteria)
  • •M79.3: Panniculitis, unspecified (localized inflammation without joint involvement)
  • •M25.50: Pain in unspecified joint (symptom without inflammatory evidence)
  • •M19.90: Unspecified osteoarthritis, unspecified site (degenerative versus inflammatory)

Child Codes

M06.0Rheumatoid arthritis without rheumatoid factor
M06.1Adult-onset Still's disease
HCC 93
M06.2Rheumatoid bursitis
M06.3Rheumatoid nodule
M06.4Inflammatory polyarthropathy
HCC 94
M06.8Other specified rheumatoid arthritis
M06.9Rheumatoid arthritis, unspecified
HCC 93

Code Hierarchy

└M06Other rheumatoid arthritis└M06.4Inflammatory polyarthropathy
└M06.4Inflammatory polyarthropathy

Because M06.4 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.

M06.4 maps to CMS-HCC V28 category 94, Systemic Lupus Erythematosus and Other Specified Systemic Connective Tissue Disorders. See the ICD-10 to HCC mapping hub for how the V28 crosswalk works. Because M06.4 carries a payment HCC, you can see what it adds to a RAF score and check the documentation the chart needs before it is submitted.

More on M06.4

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