M87.9 ICD-10-CM Code: Osteonecrosis, unspecified
HCC Buddy Code Card
Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.
FY 2026 Apr update / Diseases of the musculoskeletal system and connective tissue (M00-M99) / Other osteopathies (M86-M90)
M87.9
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceOsteonecrosis, unspecified
Death of bone tissue when the specific cause and location are not documented or determined. This is the least specific osteonecrosis code.
Buddy Insight
Unspecified osteonecrosis represents the most general category of avascular bone death when specific location and cause are not documented.
CMS-HCC V28
MappedHCC 92
RAF 0.479
CMS-HCC V24
MappedHCC 39
RAF 0.401
ACA/HHS
MappedHCC 55
Varies by metal level
ESRD/PACE
MappedHCC 39
RAF 0.092
RXHCC
MappedHCC 80
RAF 0.204
Code Book Path
Inclusion Terms
Official- Necrosis of bone NOS
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for M87.9 in this effective period.
Related Child Codes
Includes
Official- avascular necrosis of bone
Excludes 1
Official- juvenile osteonecrosis (M91-M92)
- osteochondropathies (M90-M93)
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for M87.9 in this effective period.
Use Additional
Official- code to identify major osseous defect, if applicable (M89.7-)
Code Also
OfficialICD-10-CM does not list Code Also instructions for M87.9 in this effective period.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →
Is M87.9 an HCC code?
Yes. M87.9 (Osteonecrosis, unspecified) maps to Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis under the CMS-HCC V28 risk adjustment model (and Bone/Joint/Muscle Infections/Necrosis under V24), with a community non-dual aged RAF of 0.479. It is billable for payment year 2026.
Coder answer: M87.9 is billable and maps to V28 HCC 92, Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- M87.9
- Description
- Osteonecrosis, unspecified
- HCC (V28)
- HCC 92 — Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis
- RAF
- 0.479
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
Each model's RAF is its CMS base weight for that model's standard population, so weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. 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.
Work M87.9 in the Code Book — tabular path, V28 RAF, and MEAT checklist →
MEAT Criteria for M87.9
For M87.9 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 M87.9 during that encounter, not just copy-forwarded from a problem list.
Coder workflow notes
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What This Code Means
M87.9 is the ICD-10-CM diagnosis code for osteonecrosis, unspecified. Death of bone tissue when the specific cause and location are not documented or determined. This is the least specific osteonecrosis code. M87.9 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, M87.9 maps to Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis (HCC 92) with a community, non-dual, aged base RAF weight of 0.479. Under the older CMS-HCC V24 model, M87.9 maps to Bone/Joint/Muscle Infections/Necrosis (HCC 39) with a community, non-dual, aged base RAF weight of 0.401. 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 M87.9 when the provider wording supports osteonecrosis, unspecified. Check the FY2026 tabular notes and the full code path before the final code choice. Because M87.9 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 M87.9 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use M87.9 when the provider wording supports osteonecrosis, unspecified. Check the FY2026 tabular notes and the full code path before the final code choice.
- •For this DOS, capture the provider's current assessment and the care action documented for osteonecrosis, unspecified. Keep the checklist tied to the note.
- •Do not swap M87.9 with M87.0. The FY2026 tabular describes M87.0 as idiopathic aseptic necrosis of bone. Follow the documented detail.
- •M87.9 maps to V28 HCC 92, Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis. The mapping does not replace the documentation review. The code still has to match the note.
- •Ask Buddy to show the official notes for M87.9 or compare its code path with M87.0.
Clinical Significance
Unspecified osteonecrosis represents the most general category of avascular bone death when specific location and cause are not documented. This diagnosis indicates chronic bone pathology requiring ongoing management but lacks the specificity needed for optimal care planning.
Documentation Requirements
- ✓Documentation of osteonecrosis without site or cause specification
- ✓Basic imaging evidence confirming bone death
- ✓General exclusion of acute traumatic causes
- ✓Functional assessment appropriate to patient presentation
- ✓Basic pain evaluation and symptom documentation
- ✓Screening for common underlying conditions
- ✓General treatment plan and monitoring strategy
- ✓Plans for more specific diagnostic workup if needed
Commonly Confused Codes
- •M87.30: Drug-induced osteonecrosis requires medication identification
- •M87.10: Post-traumatic osteonecrosis needs trauma history
- •M87.00: Idiopathic osteonecrosis implies workup excluding other causes
- •M89.9: Unspecified bone disorder is broader than osteonecrosis
- •M25.50: Joint pain is symptomatic, not structural bone death