M86.649
BillableOther chronic osteomyelitis, unspecified hand
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is M86.649 an HCC code?
Yes. M86.649 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 M86.649
For M86.649 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 M86.649 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
M86.649 is the ICD-10-CM diagnosis code for other chronic osteomyelitis, unspecified hand. A chronic bone infection in the hand where the specific side (left or right) is not specified or documented. M86.649 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, M86.649 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, M86.649 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.
Use this code only when laterality is truly unspecified in the medical record. Because M86.649 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 M86.649 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use this code only when laterality is truly unspecified in the medical record
- •Query provider to determine which hand is affected for more accurate coding
Clinical Significance
Other chronic osteomyelitis of unspecified hand represents a persistent bone infection affecting the hand structures without laterality specification. This condition significantly impacts fine motor function, grip strength, and activities of daily living, requiring prolonged treatment and rehabilitation while the unspecified nature may limit targeted therapeutic approaches and functional outcome planning.
Documentation Requirements
- ✓Clear documentation of chronic osteomyelitis diagnosis
- ✓Evidence of hand bone involvement without laterality specified
- ✓Confirmation of chronic duration and persistence
- ✓Laboratory studies supporting ongoing infection
- ✓Imaging studies demonstrating hand bone infection
- ✓Treatment history including antibiotic therapy
- ✓Assessment of hand function and fine motor abilities
- ✓Documentation of impact on activities of daily living