M87.849
BillableOther osteonecrosis, unspecified finger(s)
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M87.849 an HCC code?
Yes. M87.849 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 M87.849
For M87.849 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 M87.849 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M87.849 is the ICD-10-CM diagnosis code for other osteonecrosis, unspecified finger(s). Death of bone tissue in finger(s) when the specific hand (left or right) is not documented or cannot be determined. M87.849 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, M87.849 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, M87.849 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 only when laterality is truly unspecified; query provider for clarification when possible. Because M87.849 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 M87.849 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use only when laterality is truly unspecified; query provider for clarification when possible
- •Review imaging reports which may indicate side-specific involvement
Clinical Significance
Unspecified finger osteonecrosis represents a chronic bone condition with potential for functional disability and ongoing care requirements. This diagnosis is significant for risk adjustment as it indicates complex orthopedic management needs and potential requirement for specialized interventions.
Documentation Requirements
- ✓Documentation of osteonecrosis affecting finger bones (phalanges)
- ✓Specification that the condition is from causes other than idiopathic or traumatic
- ✓Evidence that laterality (right or left) is not specified or cannot be determined
- ✓Imaging studies confirming bone necrosis in finger structures
- ✓Clinical symptoms including finger pain, stiffness, and functional impairment
- ✓Exclusion of infectious or drug-induced causes
- ✓Assessment of impact on hand function and activities of daily living
- ✓Provider documentation of treatment approach and monitoring needs
Commonly Confused Codes
- •M87.049 — Idiopathic aseptic necrosis of unspecified finger(s) - specifically idiopathic cause
- •M87.844/M87.845 — Other osteonecrosis of right/left finger(s) - when laterality is actually documented
- •M86.849 — Other osteomyelitis, unspecified finger(s) - infectious condition rather than necrosis
- •S62.609A — Fracture of unspecified phalanx of unspecified finger - acute trauma rather than chronic condition
- •M20.019 — Mallet finger of unspecified finger(s) - tendon injury rather than bone necrosis