M06.879
BillableOther specified rheumatoid arthritis, unspecified ankle and foot
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M06.879 an HCC code?
Yes. M06.879 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
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 M06.879
For M06.879to 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 M06.879 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M06.879 is the ICD-10-CM diagnosis code for other specified rheumatoid arthritis, unspecified ankle and foot. A form of rheumatoid arthritis affecting the ankle and foot when the specific side (left or right) is not documented or is bilateral. M06.879 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, M06.879 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, M06.879 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.
Use this code only when ankle and foot involvement is confirmed but laterality is not specified. Because M06.879 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 M06.879 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 ankle and foot involvement is confirmed but laterality is not specified
- •Query provider documentation if bilateral ankle and foot involvement is present to determine appropriate coding
Clinical Significance
Other specified rheumatoid arthritis of unspecified ankle and foot indicates a distinct RA variant when laterality is not documented. This condition affects weight-bearing joints with potential for significant functional limitations and mobility issues.
Documentation Requirements
- ✓Confirmed rheumatoid arthritis diagnosis
- ✓Specific documentation of ankle and foot involvement
- ✓Documentation that laterality is unspecified or bilateral
- ✓Description of the specific type of RA manifestation
- ✓Assessment of ankle and foot function
- ✓Laboratory evidence supporting RA diagnosis
- ✓Disease activity monitoring and assessment
- ✓Treatment plan and management approach