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M86.129 ICD-10-CM Code: Other acute osteomyelitis, unspecified humerus

M86.129 maps to CMS-HCC V28 92. A source-labeled RAF reference is available. Documentation must support MEAT. MEAT criteria · RAF Calculator · free HCC coding tools

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FY 2026 Apr update / Diseases of the musculoskeletal system and connective tissue (M00-M99) / Other osteopathies (M86-M90)

M86.129

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Other acute osteomyelitis, unspecified humerus

A sudden bone infection in the upper arm bone (humerus) where the specific side (left or right) is not specified or documented.

Buddy the Bee presenting code insight

Buddy Insight

Acute osteomyelitis of unspecified humerus represents incomplete documentation of a serious bone infection requiring immediate intervention.

CMS-HCC V28

HCC 92

Code-level coefficient reference

CMS-HCC V24

Historical

Historical

Not used for CY2026 payment

ACA/HHS

HCC 055

Code-level coefficient reference

ESRD/PACE

HCC 39

Code-level coefficient reference

RXHCC

N/A

—

Not mapped

Code Book Path

Official
M86.1Other acute osteomyelitis
M86.12Other acute osteomyelitis, humerus
M86.129Other acute osteomyelitis, unspecified humerus

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for M86.129 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for M86.129 in this effective period.

Related Child Codes

Official
M86.121Other acute osteomyelitis, right humerus
M86.122Other acute osteomyelitis, left humerus

Includes

Official

ICD-10-CM does not list Includes notes for M86.129 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for M86.129 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for M86.129 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for M86.129 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for M86.129 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance
Documentation of humerus involvement without laterality specification
Clinical evidence of acute bone infection onset
Imaging confirmation of osteomyelitis in humeral bone
Laboratory markers of active infection

MEAT Support

HCC Buddy guidance
Documentation of humerus involvement without laterality specification
Clinical evidence of acute bone infection onset
Imaging confirmation of osteomyelitis in humeral bone
Laboratory markers of active infection

Audit Caution

HCC Buddy guidance
Using unspecified code when laterality is documented elsewhere in record
Failing to query provider for missing laterality information
Confusing timeline classifications (acute vs subacute vs chronic)
Missing opportunity to use more specific right/left codes

Common Mistakes

HCC Buddy guidance
M86109 — Acute hematogenous osteomyelitis of unspecified humerus (blood-borne)
M86629 — Chronic osteomyelitis with draining sinus of unspecified humerus
M86229 — Subacute osteomyelitis of unspecified humerus
M25519 — Pain in unspecified shoulder (symptom only)

Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →

Is M86.129 an HCC code?

Yes. M86.129 (Other acute osteomyelitis, unspecified humerus) maps to HCC 92, Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.479. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.

Coder answer: M86.129 is billable and maps to V28 HCC 92, Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.

Code
M86.129
Description
Other acute osteomyelitis, unspecified humerus
HCC (V28)
HCC 92 — Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis
RAF reference coefficient
0.479
Billable
Yes
Payment year
2026

HCC Category Mapping

V28HCC 92, Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis
0.479
ESRDHCC 39, Bone/Joint/Muscle Infections/Necrosis
Not separately weighted

These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.

Work M86.129 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT Criteria for M86.129

For M86.129 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 M86.129 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

M86.129 is the ICD-10-CM diagnosis code for other acute osteomyelitis, unspecified humerus. A sudden bone infection in the upper arm bone (humerus) where the specific side (left or right) is not specified or documented. M86.129 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, M86.129 maps to Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis (HCC 92) with a source-labeled community, non-dual, aged reference coefficient of 0.479. No V24 mapping is shown for M86.129; use the applicable model and payment year when reviewing the V28 mapping. 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. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.

Use this code only when laterality cannot be determined from documentation; query provider if possible for specificity. Because M86.129 maps to an HCC category, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) before the diagnosis is used for risk adjustment. 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, source-labeled coefficient references, and MEAT documentation criteria for M86.129 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 cannot be determined from documentation; query provider if possible for specificity
  • •This is a less specific code; attempt to clarify which arm is affected before defaulting to unspecified

Clinical Significance

Acute osteomyelitis of unspecified humerus represents incomplete documentation of a serious bone infection requiring immediate intervention. This diagnosis should prompt queries for laterality to ensure accurate coding and appropriate treatment planning.

Documentation Requirements

  • ✓Documentation of humerus involvement without laterality specification
  • ✓Clinical evidence of acute bone infection onset
  • ✓Imaging confirmation of osteomyelitis in humeral bone
  • ✓Laboratory markers of active infection
  • ✓Exclusion of hematogenous spread as primary etiology
  • ✓Treatment response documentation
  • ✓Physician query for laterality when possible
  • ✓Causative organism identification if available

Commonly Confused Codes

  • •M86109: Acute hematogenous osteomyelitis of unspecified humerus (blood-borne)
  • •M86629: Chronic osteomyelitis with draining sinus of unspecified humerus
  • •M86229: Subacute osteomyelitis of unspecified humerus
  • •M25519: Pain in unspecified shoulder (symptom only)
  • •M86121/M86122: Right/left specific codes when laterality is documented

Child Codes

M86.121Other acute osteomyelitis, right humerus
HCC 92
M86.122Other acute osteomyelitis, left humerus
HCC 92
M86.129Other acute osteomyelitis, unspecified humerus
HCC 92

Code Hierarchy

└M86Osteomyelitis└M86.1Other acute osteomyelitis└M86.12Other acute osteomyelitis, humerus└M86.129Other acute osteomyelitis, unspecified humerus
└M86.129Other acute osteomyelitis, unspecified humerus

Because M86.129 maps to an HCC category, the documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) before the diagnosis is used for risk adjustment.

M86.129 maps to CMS-HCC V28 category 92, Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis. See the ICD-10 to HCC mapping hub for how the V28 crosswalk works. The mapping identifies a payment HCC category for M86.129. Review its source-labeled HCC coefficient above, check the RAF Calculator with complete member context for CMS-HCC V28 PY2026, and confirm the documentation the chart needs before the code is submitted. HCC Buddy shows no RAF score unless every required source and calculation check passes.

Work M86.129 in HCC Buddy

Open M86.129 in the Code Book for the full Index-to-Tabular path, MEAT checklist, and V28 HCC mapping, or in the Encoder to code from a keyword search. Pro includes 7 days to try everything, no card required.

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