M87.073 ICD-10-CM Code: Idiopathic aseptic necrosis of unspecified ankle
HCC Buddy Code Card
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FY 2026 Apr update / Diseases of the musculoskeletal system and connective tissue (M00-M99) / Other osteopathies (M86-M90)
M87.073
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceIdiopathic aseptic necrosis of unspecified ankle
Death of bone tissue in the ankle without infection and without a known cause, when the side is not specified.
Buddy Insight
Idiopathic aseptic necrosis of unspecified ankle represents bone death without infection in ankle structures where laterality is not documented.
CMS-HCC V28
MappedHCC 92
RAF 0.209
CMS-HCC V24
MappedHCC 39
RAF 0.482
ACA/HHS
00
RAF 0
ESRD/PACE
MappedHCC 39
RAF 0.0
RXHCC
MappedHCC 80
RAF 0.0
Code Trumping
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Code Book Path
Inclusion Terms
Official- Idiopathic aseptic necrosis of metatarsus, tarsus, and phalanges of toes
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for M87.073 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for M87.073 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for M87.073 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for M87.073 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for M87.073 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for M87.073 in this effective period.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.
Is M87.073 an HCC code?
Yes. M87.073 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 M87.073
For M87.073to 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 M87.073 during that encounter, not just copy-forwarded from a problem list.
What This Code Means
M87.073 is the ICD-10-CM diagnosis code for idiopathic aseptic necrosis of unspecified ankle. Death of bone tissue in the ankle without infection and without a known cause, when the side is not specified. M87.073 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, M87.073 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, M87.073 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.
This is a default code when ankle involvement is documented but laterality is unclear. Because M87.073 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 M87.073 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •This is a default code when ankle involvement is documented but laterality is unclear
- •Always attempt to clarify laterality with the provider to assign a more specific code
Clinical Significance
Idiopathic aseptic necrosis of unspecified ankle represents bone death without infection in ankle structures where laterality is not documented. This condition threatens ankle joint integrity and weight-bearing function, requiring specialized orthopedic evaluation and treatment to prevent progression to joint collapse and preserve ambulation capacity.
Documentation Requirements
- ✓Clear documentation of ankle aseptic necrosis
- ✓Evidence supporting idiopathic etiology
- ✓Imaging studies confirming bone necrosis in ankle
- ✓Clinical explanation for unspecified laterality
- ✓Exclusion of infectious or traumatic causes
- ✓Assessment of ankle stability and function
- ✓Treatment plan for joint preservation
- ✓Documentation ruling out other ankle pathology