M87.871
BillableOther osteonecrosis, right ankle
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M87.871 an HCC code?
Yes. M87.871 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 M87.871
For M87.871 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 M87.871 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M87.871 is the ICD-10-CM diagnosis code for other osteonecrosis, right ankle. Death of bone tissue in the right ankle joint due to causes other than trauma or radiation. M87.871 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, M87.871 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, M87.871 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.
Ensure right ankle is clearly documented; ankle osteonecrosis may involve talus or other ankle bones. Because M87.871 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 M87.871 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Ensure right ankle is clearly documented; ankle osteonecrosis may involve talus or other ankle bones
- •Clarify which specific ankle bone is affected if documentation permits more specificity
Clinical Significance
Right ankle osteonecrosis represents avascular bone death in a critical weight-bearing joint, potentially leading to joint collapse and severe functional impairment. This condition requires aggressive management to preserve joint function and prevent the need for ankle replacement.
Documentation Requirements
- ✓Specific documentation of right ankle involvement
- ✓Advanced imaging showing osteonecrosis (MRI preferred for early detection)
- ✓Exclusion of trauma, infection, and radiation as precipitating causes
- ✓Weight-bearing status and ambulatory limitations documented
- ✓Pain level assessment using standardized scales
- ✓Evaluation for underlying predisposing conditions
- ✓Orthopedic consultation and treatment recommendations
- ✓Activity restriction protocols and compliance monitoring