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M86.221 ICD-10-CM Code: Subacute osteomyelitis, right humerus

M86.221 maps to CMS-HCC V28 92 (RAF 0.479). Documentation must support MEAT. MEAT criteria · RAF calculator · HCC coding software

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

M86.221

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

Subacute osteomyelitis, right humerus

A bone infection in the right upper arm bone (humerus) that develops gradually over weeks to months, causing inflammation and potential bone damage.

Buddy the Bee presenting code insight

Buddy Insight

Subacute osteomyelitis of the right humerus represents a bone infection with gradual onset affecting the major upper arm bone over weeks to months.

CMS-HCC V28

HCC 92

RAF 0.479

CMS-HCC V24

HCC 39

RAF 0.401

ACA/HHS

HCC 55

Varies by metal level

ESRD/PACE

HCC 39

RAF 0.092

RXHCC

N/A

—

Not mapped

Code Book Path

Official
M86.2Subacute osteomyelitis
M86.22Subacute osteomyelitis, humerus
M86.221Subacute osteomyelitis, right humerus

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for M86.221 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for M86.221 in this effective period.

Related Child Codes

Official
M86.222Subacute osteomyelitis, left humerus
M86.229Subacute osteomyelitis, unspecified humerus

Includes

Official

ICD-10-CM does not list Includes notes for M86.221 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for M86.221 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for M86.221 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for M86.221 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for M86.221 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance
Specific identification of right humerus involvement
Documentation of subacute infection timeline
Clinical evidence of humeral bone infection
Imaging confirmation of osteomyelitis in right humerus

MEAT Support

HCC Buddy guidance
Specific identification of right humerus involvement
Documentation of subacute infection timeline
Clinical evidence of humeral bone infection
Imaging confirmation of osteomyelitis in right humerus

Audit Caution

HCC Buddy guidance
Confusing subacute with acute or chronic phases
Missing the intermediate timeline significance
Not documenting functional assessment adequately
Confusing with traumatic conditions

Common Mistakes

HCC Buddy guidance
M86121 — Other acute osteomyelitis of right humerus
M86621 — Chronic osteomyelitis with draining sinus of right humerus
M86321 — Chronic multifocal osteomyelitis of right humerus
M25511 — Pain in right shoulder

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 M86.221 an HCC code?

Yes. M86.221 (Subacute osteomyelitis, right humerus) maps to Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis under the CMS-HCC V28 risk adjustment model (and Bone/Joint/Muscle Infections/Necrosis under V24), with a community non-dual aged RAF of 0.479. It is billable for payment year 2026.

Coder answer: M86.221 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
M86.221
Description
Subacute osteomyelitis, right humerus
HCC (V28)
HCC 92 — Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis
RAF
0.479
Billable
Yes
Payment year
2026

HCC Category Mapping

V28HCC 92, Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis
0.479
V24HCC 39, Bone/Joint/Muscle Infections/Necrosis
0.401
ESRDHCC 39, Bone/Joint/Muscle Infections/Necrosis
0.092

Each model's RAF is its CMS base weight for that model's standard population, so 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 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.

Work M86.221 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for M86.221

For M86.221 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 M86.221 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

M86.221 is the ICD-10-CM diagnosis code for subacute osteomyelitis, right humerus. A bone infection in the right upper arm bone (humerus) that develops gradually over weeks to months, causing inflammation and potential bone damage. M86.221 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, M86.221 maps to Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis (HCC 92) with a community, non-dual, aged base RAF weight of 0.479. Under the older CMS-HCC V24 model, M86.221 maps to Bone/Joint/Muscle Infections/Necrosis (HCC 39) with a community, non-dual, aged base RAF weight of 0.401. 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.

Verify the infection site is specifically the humerus and not the shoulder joint itself. Because M86.221 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 M86.221 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •Verify the infection site is specifically the humerus and not the shoulder joint itself
  • •Document the specific location on the humerus (proximal, shaft, or distal) if available for additional specificity

Clinical Significance

Subacute osteomyelitis of the right humerus represents a bone infection with gradual onset affecting the major upper arm bone over weeks to months. This intermediate phase infection requires monitoring to prevent progression to chronic osteomyelitis and preserve upper extremity function.

Documentation Requirements

  • ✓Specific identification of right humerus involvement
  • ✓Documentation of subacute infection timeline
  • ✓Clinical evidence of humeral bone infection
  • ✓Imaging confirmation of osteomyelitis in right humerus
  • ✓Laboratory evidence of ongoing bone infection
  • ✓Assessment of arm function and range of motion
  • ✓Documentation of symptom progression
  • ✓Treatment plan to prevent chronic conversion

Commonly Confused Codes

  • •M86121: Other acute osteomyelitis of right humerus
  • •M86621: Chronic osteomyelitis with draining sinus of right humerus
  • •M86321: Chronic multifocal osteomyelitis of right humerus
  • •M25511: Pain in right shoulder
  • •S42.301A: Unspecified fracture of shaft of right humerus

Child Codes

M86.221Subacute osteomyelitis, right humerus
HCC 92
M86.222Subacute osteomyelitis, left humerus
HCC 92
M86.229Subacute osteomyelitis, unspecified humerus
HCC 92

Code Hierarchy

└M86Osteomyelitis└M86.2Subacute osteomyelitis└M86.22Subacute osteomyelitis, humerus└M86.221Subacute osteomyelitis, right humerus
└M86.221Subacute osteomyelitis, right humerus

Because M86.221 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score.

M86.221 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. Because M86.221 carries a payment HCC, you can see what it adds to a RAF score and check the documentation the chart needs before it is submitted.

Work M86.221 in HCC Buddy

Open M86.221 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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