M87.371
BillableOther secondary osteonecrosis, right ankle
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M87.371 an HCC code?
Yes. M87.371 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 M87.371
For M87.371 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 M87.371 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M87.371 is the ICD-10-CM diagnosis code for other secondary osteonecrosis, right ankle. Death of bone tissue in the right ankle caused by an underlying condition or treatment such as radiation, corticosteroids, or previous trauma. M87.371 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, M87.371 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, M87.371 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.
Confirm right ankle is the correct site; ankle osteonecrosis may affect talus or other ankle bones. Because M87.371 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 M87.371 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Confirm right ankle is the correct site; ankle osteonecrosis may affect talus or other ankle bones
- •Link this code to the documented secondary cause (e.g., post-radiation, post-traumatic) for complete clinical picture
Clinical Significance
This diagnosis represents secondary osteonecrosis of the right ankle caused by underlying conditions such as radiation, corticosteroids, or previous trauma, which can significantly impact mobility and weight-bearing function. It requires management of the underlying cause and monitoring for joint collapse.
Documentation Requirements
- ✓Documentation of osteonecrosis affecting right ankle bones
- ✓Identification of underlying cause (e.g., corticosteroid use, radiation therapy, previous trauma)
- ✓Imaging findings confirming ankle bone necrosis (MRI, X-ray, CT)
- ✓Clinical symptoms such as ankle pain, swelling, or stiffness
- ✓Specific ankle bones affected (talus, calcaneus, etc.)
- ✓Functional limitations affecting walking and weight-bearing
- ✓Duration and progression of condition
- ✓Treatment history including conservative and surgical options
Commonly Confused Codes
- •M87.372 — Other secondary osteonecrosis, left ankle (different laterality)
- •M87.373 — Other secondary osteonecrosis, unspecified ankle (laterality not specified)
- •M86.171 — Chronic osteomyelitis of right ankle (infection vs necrosis)
- •S93.401A — Sprain of unspecified ligament of right ankle (acute injury vs necrosis)
- •M19.071 — Primary osteoarthritis of right ankle (arthritis vs necrosis)