M87.879
BillableOther osteonecrosis, unspecified toe(s)
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M87.879 an HCC code?
Yes. M87.879 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 M87.879
For M87.879 to 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 M87.879 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M87.879 is the ICD-10-CM diagnosis code for other osteonecrosis, unspecified toe(s). Death of bone tissue in toe(s) of unspecified side due to causes other than trauma, infection, or radiation. This can cause pain and difficulty walking or wearing shoes. M87.879 sits in the ICD-10-CM chapter for diseases of the musculoskeletal system and connective tissue (m00-m99), within the section covering other osteopathies (m86-m90).
Under the CMS-HCC V28 risk adjustment model, M87.879 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, M87.879 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 laterality (right vs. left) is not documented; query provider if laterality can be determined. Because M87.879 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 M87.879 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 laterality (right vs. left) is not documented; query provider if laterality can be determined
- •This is a less specific code; attempt to obtain laterality information for more precise coding
Clinical Significance
Unspecified toe osteonecrosis represents avascular bone death in toe bones without documented laterality, potentially indicating bilateral involvement or incomplete documentation. This condition can affect gait stability and balance, requiring comprehensive foot care management.
Documentation Requirements
- ✓Documentation of toe osteonecrosis without side specification
- ✓Bilateral toe assessment if both sides potentially affected
- ✓Exclusion of trauma, infection, and radiation as causes
- ✓Comprehensive gait and balance evaluation
- ✓Pain assessment and functional impact on ambulation
- ✓Underlying disease evaluation (diabetes, peripheral vascular disease)
- ✓Coordinated podiatric and orthopedic care
- ✓Prevention strategies for secondary complications
Commonly Confused Codes
- •M87.379 — Drug-induced osteonecrosis requires causative medication documentation
- •M87.179 — Traumatic osteonecrosis needs clear injury history
- •M87.079 — Idiopathic osteonecrosis lacks identifiable underlying etiology
- •S92.509A — Unspecified toe fracture is acute injury
- •M20.90 — Unspecified acquired toe deformity is structural, not necrotic