M02.879
BillableOther reactive arthropathies, unspecified ankle and foot
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M02.879 an HCC code?
Yes. M02.879 maps to Bone/Joint/Muscle Infections/Necrosis under the CMS-HCC V28 risk adjustment model (and Bone/Joint/Muscle Infections/Necrosis 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 M02.879
For M02.879to 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 M02.879 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M02.879 is the ICD-10-CM diagnosis code for other reactive arthropathies, unspecified ankle and foot. Joint inflammation in the ankle and foot that develops as a reaction to an infection or other trigger, but the specific side (right or left) is not identified. M02.879 sits in the ICD-10-CM chapter for diseases of the musculoskeletal system and connective tissue (m00-m99), within the section covering infectious arthropathies (m00-m02).
Under the CMS-HCC V28 risk adjustment model, M02.879 maps to Bone/Joint/Muscle Infections/Necrosis (HCC 92) with a community, non-dual, aged base RAF weight of 0.209. Under the older V24 model, M02.879 mapped to the same category but with a base RAF weight of 0.482 — 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 bilateral involvement is present or when laterality cannot be determined from documentation. Because M02.879 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 M02.879 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
Clinical Significance
This diagnosis represents reactive arthropathy affecting the ankle and foot when laterality is not specified in documentation. The unspecified nature may indicate bilateral involvement, incomplete clinical assessment, or inadequate documentation, potentially affecting treatment precision and functional assessment.
Documentation Requirements
- ✓Clinical evidence of ankle and/or foot joint inflammation (swelling, pain, stiffness)
- ✓Documentation of reactive nature - inflammation secondary to remote infection
- ✓Confirmation that ankle/foot laterality is truly unspecified or bilateral involvement
- ✓Evidence ruling out direct septic arthritis or other infectious arthropathies
- ✓Documentation of triggering infection or infectious process (if identified)
- ✓Physical examination findings consistent with ankle/foot arthritis
- ✓Exclusion of other arthropathy types (rheumatoid, osteoarthritis, crystal arthropathy)
- ✓Assessment of functional impact on ambulation and balance
Commonly Confused Codes
- •M02.871 — Other reactive arthropathies, right ankle and foot (when laterality documented)
- •M02.872 — Other reactive arthropathies, left ankle and foot (when laterality documented)
- •M00.079 — Staphylococcal arthritis, unspecified ankle and foot (infectious vs reactive)
- •M06.079 — Rheumatoid arthritis, unspecified ankle and foot (autoimmune vs reactive)
- •M25.579 — Pain in unspecified ankle and foot (symptom vs specific arthropathy diagnosis)