What is ICD-10 code M12.00?

M12.00 is the ICD-10-CM diagnosis code for Chronic postrheumatic arthropathy [Jaccoud], unspecified site. A chronic joint condition that develops after rheumatic fever, causing joint deformities and stiffness without permanent damage to the joint structure. M12.00 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. M12.00 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. M12.00 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. M12.00 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.

Which HCC does M12.00 map to under V28?

M12.00 maps to CMS-HCC V28 HCC 94 (Systemic Lupus Erythematosus and Other Specified Systemic Connective Tissue Disorders). The category numbers, labels, and conditions come from the CMS-HCC V28 model file for payment year 2026.

2026 ICD-10-CM M12.00: Chronic postrheumatic

M12.00 maps to CMS-HCC V28 94. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · HCC Buddy coding tools

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Code lookupM12.00

Effective 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)

M12.00

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

Chronic postrheumatic arthropathy [Jaccoud], unspecified site

A chronic joint condition that develops after rheumatic fever, causing joint deformities and stiffness without permanent damage to the joint structure.

Buddy Insight

Chronic postrheumatic arthropathy (Jaccoud's arthropathy) is a non-erosive inflammatory condition that occurs as a late sequela of rheumatic fever, causing reversible joint deformities.

Overview Risk Models Code Book Documentation Audit Notes Edition comparison

CMS-HCC V28

Mapped

HCC 94

Systemic Lupus Erythematosus ...

Code-level coefficient reference

CMS-HCC V24

Historical

Not used for standard CY2026 Medicare Advantage payment. Select a historical period to review V24.

Not used for CY2026 payment

ACA/HHS

Mapped

HCC 057

HHS-HCC 057 adult, RAF varies...

Code-level coefficient reference

ESRD/PACE

Mapped

HCC 40

Rheumatoid Arthritis and Infl...

Code-level coefficient reference

RXHCC

Mapped

HCC 83

Rheumatoid Arthritis and Othe...

Code-level coefficient reference

Code Book Path

Official

M12Other and unspecified arthropathy M12.0Chronic postrheumatic arthropathy [Jaccoud]M12.00Chronic postrheumatic arthropathy [Jaccoud], unspecified site

Inclusion Terms

Official

No inclusion terms are included in this display for M12.00. Check the code and parent instructions in the Code Book.

Excludes 2

Official

arthropathic psoriasis (L40.5-)Inherited from M00-M99
certain conditions originating in the perinatal period (P04-P96)Inherited from M00-M99
certain infectious and parasitic diseases (A00-B99)Inherited from M00-M99
compartment syndrome (traumatic) (T79.A-)Inherited from M00-M99
complications of pregnancy, childbirth and the puerperium (O00-O9A)Inherited from M00-M99
congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)Inherited from M00-M99
endocrine, nutritional and metabolic diseases (E00-E88)Inherited from M00-M99
injury, poisoning and certain other consequences of external causes (S00-T88)Inherited from M00-M99
neoplasms (C00-D49)Inherited from M00-M99
symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)Inherited from M00-M99

Related Codes

Official

M12.01Chronic postrheumatic arthropathy [Jaccoud], shoulder M12.02Chronic postrheumatic arthropathy [Jaccoud], elbow M12.03Chronic postrheumatic arthropathy [Jaccoud], wrist M12.04Chronic postrheumatic arthropathy [Jaccoud], hand M12.05Chronic postrheumatic arthropathy [Jaccoud], hip

Includes

Official

No Includes notes are included in this display for M12.00. Check the code and parent instructions in the Code Book.

Excludes 1

Official

arthrosis (M15-M19)Inherited from M12
cricoarytenoid arthropathy (J38.7)Inherited from M12

Code First

Official

No Code First sequencing instructions are included in this display for M12.00. Check the code and parent instructions in the Code Book.

Use Additional

Official

No Use Additional Code instructions are included in this display for M12.00. Check the code and parent instructions in the Code Book.

Code Also

Official

No Code Also instructions are included in this display for M12.00. Check the code and parent instructions in the Code Book.

Buddy Documentation Tip

HCC Buddy guidance

History of rheumatic fever or rheumatic heart disease

Evidence of chronic joint deformities (reducible/non-fixed)

Joint site unspecified in documentation

Absence of joint erosions on imaging

MEAT Support

HCC Buddy guidance

History of rheumatic fever or rheumatic heart disease

Evidence of chronic joint deformities (reducible/non-fixed)

Joint site unspecified in documentation

Absence of joint erosions on imaging

Audit Caution

HCC Buddy guidance

Using this code when specific joint sites are documented

Confusing with erosive rheumatoid arthritis

Not establishing history of rheumatic fever

Coding without evidence of joint deformities

Common Mistakes

HCC Buddy guidance

M12.01-M12.09 — Use when specific joint site is documented

M05.9 — Rheumatoid arthritis has joint erosions

M32.10 — SLE arthropathy has different underlying cause

M25.9 — Joint disorder unspecified without rheumatic fever history

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 M12.00 an HCC code?

Yes. M12.00 (Chronic postrheumatic arthropathy [Jaccoud], unspecified site) maps to HCC 94, Systemic Lupus Erythematosus and Other Specified Systemic Connective Tissue Disorders under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.268. 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: M12.00 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: M12.00
Description: Chronic postrheumatic arthropathy [Jaccoud], unspecified site
HCC (V28): HCC 94 — Systemic Lupus Erythematosus and Other Specified Systemic Connective Tissue Disorders
RAF reference coefficient: 0.268
Billable: Yes
Payment year: 2026

HCC Category Mapping

V28HCC 94, Systemic Lupus Erythematosus and Other Specified Systemic Connective Tissue Disorders

0.268

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 M12.00 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT review for M12.00

For M12.00, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.

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

Coder workflow notes

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What This Code Means

M12.00 is the ICD-10-CM diagnosis code for chronic postrheumatic arthropathy [jaccoud], unspecified site. A chronic joint condition that develops after rheumatic fever, causing joint deformities and stiffness without permanent damage to the joint structure. M12.00 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, M12.00 maps to Systemic Lupus Erythematosus and Other Specified Systemic Connective Tissue Disorders (HCC 94) with a source-labeled community, non-dual, aged reference coefficient of 0.268. No V24 mapping is shown for M12.00; use the applicable model and payment year when reviewing the V28 mapping. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. 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.

Use this code only when the specific site of Jaccoud arthropathy is not documented or affects multiple unspecified sites. For M12.00, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. 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 M12.00 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Use this code only when the specific site of Jaccoud arthropathy is not documented or affects multiple unspecified sites
•This is a sequela of acute rheumatic fever; document the history of rheumatic fever in the patient record

Clinical Significance

Chronic postrheumatic arthropathy (Jaccoud's arthropathy) is a non-erosive inflammatory condition that occurs as a late sequela of rheumatic fever, causing reversible joint deformities. This diagnosis indicates a history of rheumatic heart disease and requires ongoing monitoring for cardiac complications.