M86.419
BillableChronic osteomyelitis with draining sinus, unspecified shoulder
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M86.419 an HCC code?
Yes. M86.419 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 M86.419
For M86.419 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 M86.419 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M86.419 is the ICD-10-CM diagnosis code for chronic osteomyelitis with draining sinus, unspecified shoulder. A long-term bone infection in the shoulder that has created an open drainage tract allowing pus or fluid to drain to the skin surface, with the specific shoulder not identified. M86.419 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, M86.419 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, M86.419 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 code requires documentation of chronicity and the presence of a draining sinus tract; verify the shoulder side is truly unspecified before using this code. Because M86.419 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 M86.419 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
Clinical Significance
Chronic osteomyelitis with draining sinus of unspecified shoulder indicates a severe bone infection with persistent drainage when laterality is not documented, representing complex disease requiring intensive management. The draining component significantly complicates treatment and increases risk for treatment failure.
Documentation Requirements
- ✓Documentation of shoulder involvement without laterality specification
- ✓Evidence of chronic infection (>6 weeks duration or recurrent)
- ✓Confirmation of active draining sinus tract
- ✓Radiographic findings consistent with chronic osteomyelitis
- ✓Clinical evidence of persistent drainage from shoulder
- ✓Laboratory evidence supporting chronic infectious process
- ✓Treatment history addressing both infection and drainage
- ✓Absence of clear laterality information in medical record