What is ICD-10 code M05.842?

M05.842 is the ICD-10-CM diagnosis code for Other rheumatoid arthritis with rheumatoid factor of left hand. A type of rheumatoid arthritis affecting the left hand in patients who test positive for rheumatoid factor, an antibody associated with this autoimmune joint disease. M05.842 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. M05.842 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. M05.842 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. M05.842 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 M05.842?

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 M05.842, 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 M05.842?

Ensure left hand is specifically documented as the affected site Hand involvement in rheumatoid arthritis often affects multiple joints; code each hand separately if both are involved Because M05.842 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.

M05.842 ICD-10 Code: Other 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 lookupM05.842Effective 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)

M05.842

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

Other rheumatoid arthritis with rheumatoid factor of left hand

A type of rheumatoid arthritis affecting the left hand in patients who test positive for rheumatoid factor, an antibody associated with this autoimmune joint disease.

Buddy Insight

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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Compare selected patient codes to show trumped or trumps impact.

Code Book Path

Official

M05.8Other rheumatoid arthritis with rheumatoid factor

M05.84Other rheumatoid arthritis with rheumatoid factor of hand

M05.842Other rheumatoid arthritis with rheumatoid factor of left hand

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for M05.842 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for M05.842 in this effective period.

Related Child Codes

Official

M05.841Other rheumatoid arthritis with rheumatoid factor of right hand

M05.849Other rheumatoid arthritis with rheumatoid factor of unspecified hand

Includes

Official

ICD-10-CM does not list Includes notes for M05.842 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for M05.842 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for M05.842 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for M05.842 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for M05.842 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Clinical diagnosis of rheumatoid arthritis clearly documented by the treating provider

Rheumatoid factor lab result status (positive or negative) consistent with the code selected

Affected joint(s) specified with laterality (right, left, or bilateral)

Current disease status: active, in remission, or chronic stable

MEAT Support

HCC Buddy guidance

Clinical diagnosis of rheumatoid arthritis clearly documented by the treating provider

Rheumatoid factor lab result status (positive or negative) consistent with the code selected

Affected joint(s) specified with laterality (right, left, or bilateral)

Current disease status: active, in remission, or chronic stable

Audit Caution

HCC Buddy guidance

Failing to verify rheumatoid factor status before selecting between M05 (seropositive) and M06 (seronegative) categories — lab results must support code selection

Coding rheumatoid arthritis based solely on a positive rheumatoid factor lab result without a clinical diagnosis from the provider — a positive rheumatoid factor alone is not sufficient to code rheumatoid arthritis

Reporting rheumatoid arthritis from past medical history without confirmation that the condition is still active, being treated, or being monitored during the current encounter

Not linking rheumatoid arthritis to all associated manifestations that may warrant additional codes, such as anemia of chronic disease or interstitial lung disease

Common Mistakes

HCC Buddy guidance

M05.7xx (Rheumatoid arthritis with rheumatoid factor without organ involvement, same site) — Use M05.7xx for the standard seropositive presentation without organ or systems involvement

M06.0xx (Rheumatoid arthritis without rheumatoid factor, same site) — Use M06.0xx when rheumatoid factor is negative

M06.9 (Rheumatoid arthritis, unspecified) — A nonspecific code that does not indicate rheumatoid factor status; avoid when rheumatoid factor status is known

M05.0x-M05.6x (Rheumatoid arthritis with organ involvement such as Felty syndrome, rheumatoid lung, vasculitis) — Use these when extra-articular manifestations are documented

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 M05.842 an HCC code?

Yes. M05.842 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 M05.842

For M05.842to 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 M05.842 during that encounter, not just copy-forwarded from a problem list.

What This Code Means

M05.842 is the ICD-10-CM diagnosis code for other rheumatoid arthritis with rheumatoid factor of left hand. A type of rheumatoid arthritis affecting the left hand in patients who test positive for rheumatoid factor, an antibody associated with this autoimmune joint disease. M05.842 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, M05.842 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, M05.842 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.

Ensure left hand is specifically documented as the affected site. Because M05.842 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 M05.842 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Ensure left hand is specifically documented as the affected site
•Hand involvement in rheumatoid arthritis often affects multiple joints; code each hand separately if both are involved

Clinical Significance

This code captures other specified manifestations of seropositive rheumatoid arthritis with positive rheumatoid factor, representing a systemic autoimmune condition with potential for progressive joint destruction and disability. Accurate capture is essential for risk adjustment as it reflects significant ongoing treatment burden including disease-modifying antirheumatic drugs, biologics, and regular laboratory monitoring.

Documentation Requirements

✓Clinical diagnosis of rheumatoid arthritis clearly documented by the treating provider
✓Rheumatoid factor lab result status (positive or negative) consistent with the code selected
✓Affected joint(s) specified with laterality (right, left, or bilateral)
✓Current disease status: active, in remission, or chronic stable
✓Current treatment plan including medications (disease-modifying antirheumatic drugs, biologics, nonsteroidal anti-inflammatory drugs)
✓Specification of the 'other' rheumatoid arthritis manifestation or feature that distinguishes it from standard presentations
✓Assessment and plan addressing rheumatoid arthritis at each encounter where it impacts care or treatment

Commonly Confused Codes

•M05.7xx (Rheumatoid arthritis with rheumatoid factor without organ involvement, same site): Use M05.7xx for the standard seropositive presentation without organ or systems involvement
•M06.0xx (Rheumatoid arthritis without rheumatoid factor, same site): Use M06.0xx when rheumatoid factor is negative
•M06.9 (Rheumatoid arthritis, unspecified): A nonspecific code that does not indicate rheumatoid factor status; avoid when rheumatoid factor status is known
•M05.0x-M05.6x (Rheumatoid arthritis with organ involvement such as Felty syndrome, rheumatoid lung, vasculitis): Use these when extra-articular manifestations are documented
•M19.x (Osteoarthritis): Osteoarthritis is a degenerative, non-autoimmune condition; do not confuse with rheumatoid arthritis which is inflammatory and autoimmune