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M05.021 ICD-10-CM Code: Felty's syndrome, right elbow

M05.021 maps to CMS-HCC V28 93. A source-labeled RAF reference is available. Documentation must support MEAT. MEAT criteria · RAF Calculator · free HCC coding tools

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

M05.021

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

Felty's syndrome, right elbow

Felty's syndrome affecting the right elbow, characterized by rheumatoid arthritis, enlarged spleen, and low white blood cell count.

Buddy the Bee presenting code insight

Buddy Insight

Felty's syndrome affecting the right elbow represents a severe systemic rheumatoid condition that combines joint inflammation with dangerous hematologic abnormalities.

CMS-HCC V28

HCC 93

Code-level coefficient reference

CMS-HCC V24

Historical

Historical

Not used for CY2026 payment

ACA/HHS

HCC 056

Code-level coefficient reference

ESRD/PACE

HCC 40

Code-level coefficient reference

RXHCC

HCC 83

Code-level coefficient reference

Code Book Path

Official
M05.0Felty's syndrome
M05.02Felty's syndrome, elbow
M05.021Felty's syndrome, right elbow

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for M05.021 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for M05.021 in this effective period.

Related Child Codes

Official
M05.022Felty's syndrome, left elbow
M05.029Felty's syndrome, unspecified elbow

Includes

Official

ICD-10-CM does not list Includes notes for M05.021 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for M05.021 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for M05.021 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for M05.021 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for M05.021 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance
Clear documentation of rheumatoid arthritis specifically affecting the right elbow
Evidence of splenomegaly through physical examination or imaging
Laboratory confirmation of neutropenia with specific cell counts
Right elbow joint involvement explicitly documented

MEAT Support

HCC Buddy guidance
Clear documentation of rheumatoid arthritis specifically affecting the right elbow
Evidence of splenomegaly through physical examination or imaging
Laboratory confirmation of neutropenia with specific cell counts
Right elbow joint involvement explicitly documented

Audit Caution

HCC Buddy guidance
Coding regular rheumatoid arthritis when the full Felty's triad is present
Using unspecified elbow code when right side is clearly documented
Missing the hematologic components that define Felty's syndrome
Failing to capture the systemic nature of the condition

Common Mistakes

HCC Buddy guidance
M05.9 — Seropositive rheumatoid arthritis without the Felty's syndrome components
M06.022 — Rheumatoid bursitis of left elbow, wrong laterality and condition type
D70.9 — Neutropenia without the rheumatoid arthritis component
M05.029 — Same condition but unspecified elbow when right is documented

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 M05.021 an HCC code?

Yes. M05.021 (Felty's syndrome, right elbow) maps to HCC 93, Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.617. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.

Coder answer: M05.021 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
M05.021
Description
Felty's syndrome, right elbow
HCC (V28)
HCC 93 — Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders
RAF reference coefficient
0.617
Billable
Yes
Payment year
2026

HCC Category Mapping

V28HCC 93, Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders
0.617
ESRDHCC 40, Rheumatoid Arthritis and Inflammatory Connective Tissue Disease
Not separately weighted
RxHCCHCC 83, Rheumatoid Arthritis and Other Inflammatory Polyarthropathy
Not separately weighted

These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. 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 context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.

Work M05.021 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT Criteria for M05.021

For M05.021 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 M05.021 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

M05.021 is the ICD-10-CM diagnosis code for felty's syndrome, right elbow. Felty's syndrome affecting the right elbow, characterized by rheumatoid arthritis, enlarged spleen, and low white blood cell count. M05.021 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, M05.021 maps to Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders (HCC 93) with a source-labeled community, non-dual, aged reference coefficient of 0.617. No V24 mapping is shown for M05.021; use the applicable model and payment year when reviewing the V28 mapping. 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. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.

Ensure documentation specifically mentions right elbow involvement. Because M05.021 maps to an HCC category, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) before the diagnosis is used for risk adjustment. 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, source-labeled coefficient references, and MEAT documentation criteria for M05.021 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •Ensure documentation specifically mentions right elbow involvement
  • •This code should not be used for bilateral or left elbow involvement

Clinical Significance

Felty's syndrome affecting the right elbow represents a severe systemic rheumatoid condition that combines joint inflammation with dangerous hematologic abnormalities. This diagnosis requires urgent attention due to the immunocompromised state from neutropenia and the potential for serious infectious complications.

Documentation Requirements

  • ✓Clear documentation of rheumatoid arthritis specifically affecting the right elbow
  • ✓Evidence of splenomegaly through physical examination or imaging
  • ✓Laboratory confirmation of neutropenia with specific cell counts
  • ✓Right elbow joint involvement explicitly documented
  • ✓Assessment of joint function and inflammatory markers
  • ✓History of recurrent infections or immune dysfunction
  • ✓Current immunosuppressive therapy and monitoring protocols
  • ✓Exclusion of other causes of neutropenia and splenomegaly

Commonly Confused Codes

  • •M05.9: Seropositive rheumatoid arthritis without the Felty's syndrome components
  • •M06.022: Rheumatoid bursitis of left elbow, wrong laterality and condition type
  • •D70.9: Neutropenia without the rheumatoid arthritis component
  • •M05.029: Same condition but unspecified elbow when right is documented
  • •K63.2: When spleen findings are misinterpreted as other abdominal conditions

Child Codes

M05.021Felty's syndrome, right elbow
HCC 93
M05.022Felty's syndrome, left elbow
HCC 93
M05.029Felty's syndrome, unspecified elbow
HCC 93

Code Hierarchy

└M05Rheumatoid arthritis with rheumatoid factor└M05.0Felty's syndrome└M05.02Felty's syndrome, elbow└M05.021Felty's syndrome, right elbow
└M05.021Felty's syndrome, right elbow

Because M05.021 maps to an HCC category, the documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) before the diagnosis is used for risk adjustment.

M05.021 maps to CMS-HCC V28 category 93, Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders. See the ICD-10 to HCC mapping hub for how the V28 crosswalk works. The mapping identifies a payment HCC category for M05.021. Review its source-labeled HCC coefficient above, check the RAF Calculator with complete member context for CMS-HCC V28 PY2026, and confirm the documentation the chart needs before the code is submitted. HCC Buddy shows no RAF score unless every required source and calculation check passes.

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