M12.012
BillableChronic postrheumatic arthropathy [Jaccoud], left shoulder
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M12.012 an HCC code?
Yes. M12.012 maps to Reactive and Specified Arthropathies under the CMS-HCC V28 risk adjustment model (and Rheumatoid Arthritis and Inflammatory Connective Tissue Disease under V24).
HCC Category Mapping
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 M12.012
For M12.012to 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 M12.012 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M12.012 is the ICD-10-CM diagnosis code for chronic postrheumatic arthropathy [jaccoud], left shoulder. A chronic joint condition affecting the left shoulder that develops after rheumatic fever, causing joint deformities and stiffness. M12.012 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, M12.012 maps to Reactive and Specified Arthropathies (HCC 94) with a community, non-dual, aged base RAF weight of 0.000. Under the older CMS-HCC V24 model, M12.012 maps to Rheumatoid Arthritis and Inflammatory Connective Tissue Disease (HCC 40) with a community, non-dual, aged base RAF weight of 0.307. 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 this code specifically when Jaccoud arthropathy is documented as affecting the left shoulder. Because M12.012 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 M12.012 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use this code specifically when Jaccoud arthropathy is documented as affecting the left shoulder
- •Verify laterality documentation to ensure accurate left-sided coding
Clinical Significance
Chronic postrheumatic arthropathy of the left shoulder is a late complication of rheumatic fever causing non-erosive joint deformities that can significantly impact daily activities and upper extremity function. This diagnosis requires coordination between rheumatology and cardiology due to associated cardiac risks.
Documentation Requirements
- ✓Established history of rheumatic fever
- ✓Specific left shoulder joint involvement documented
- ✓Evidence of chronic, reversible joint deformity
- ✓Clinical findings consistent with Jaccoud's arthropathy
- ✓Imaging showing absence of joint erosions
- ✓Assessment of left shoulder function and mobility
- ✓Concurrent cardiac evaluation and status
- ✓Timeline of symptom development post-rheumatic fever