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M86.079 ICD-10-CM Code: Acute hematogenous osteomyelitis, unspecified ankle and foot

M86.079 maps to CMS-HCC V28 92 (RAF 0.479). Documentation must support MEAT. MEAT criteria · RAF calculator · HCC Buddy coding tools

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

M86.079

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

Acute hematogenous osteomyelitis, unspecified ankle and foot

A bacterial bone infection in the ankle or foot that develops suddenly, typically spreading through the bloodstream, when the specific side (left or right) is not documented.

Buddy the Bee presenting code insight

Buddy Insight

Acute hematogenous osteomyelitis of unspecified ankle and foot represents a bloodstream-originated bone infection where laterality documentation is unavailable or unclear.

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
M86.0Acute hematogenous osteomyelitis
M86.07Acute hematogenous osteomyelitis, ankle and foot
M86.079Acute hematogenous osteomyelitis, unspecified ankle and foot

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for M86.079 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for M86.079 in this effective period.

Related Child Codes

Official
M86.071Acute hematogenous osteomyelitis, right ankle and foot
M86.072Acute hematogenous osteomyelitis, left ankle and foot

Includes

Official

ICD-10-CM does not list Includes notes for M86.079 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for M86.079 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for M86.079 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for M86.079 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for M86.079 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance
Clear documentation of acute hematogenous osteomyelitis
Identification of ankle and/or foot bone involvement
Documentation that laterality is unspecified or unknown
Clinical evidence of bone infection with associated symptoms

MEAT Support

HCC Buddy guidance
Clear documentation of acute hematogenous osteomyelitis
Identification of ankle and/or foot bone involvement
Documentation that laterality is unspecified or unknown
Clinical evidence of bone infection with associated symptoms

Audit Caution

HCC Buddy guidance
Using when laterality is documented elsewhere in medical record
Failing to confirm hematogenous versus other infection origins
Applying to soft tissue infections without bone involvement
Confusion between acute and other temporal classifications

Common Mistakes

HCC Buddy guidance
M86.071/M86.072 — Use when specific laterality is documented
M86.179 — Use for non-hematogenous acute osteomyelitis of unspecified ankle/foot
M86.679 — Use for chronic osteomyelitis of unspecified ankle/foot
L03.116/L03.117 — Use for cellulitis without bone involvement

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 M86.079 an HCC code?

Yes. M86.079 (Acute hematogenous osteomyelitis, unspecified ankle and foot) 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: M86.079 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
M86.079
Description
Acute hematogenous osteomyelitis, unspecified ankle and foot
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 M86.079 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for M86.079

For M86.079 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 M86.079 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

M86.079 is the ICD-10-CM diagnosis code for acute hematogenous osteomyelitis, unspecified ankle and foot. A bacterial bone infection in the ankle or foot that develops suddenly, typically spreading through the bloodstream, when the specific side (left or right) is not documented. M86.079 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, M86.079 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, M86.079 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.

Use this code only when laterality cannot be determined from documentation. Because M86.079 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 M86.079 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 laterality is clinically relevant but not documented

Clinical Significance

Acute hematogenous osteomyelitis of unspecified ankle and foot represents a bloodstream-originated bone infection where laterality documentation is unavailable or unclear. This serious condition requires prompt antibiotic treatment to prevent progression to chronic infection, joint destruction, or systemic complications affecting patient mobility.

Documentation Requirements

  • ✓Clear documentation of acute hematogenous osteomyelitis
  • ✓Identification of ankle and/or foot bone involvement
  • ✓Documentation that laterality is unspecified or unknown
  • ✓Clinical evidence of bone infection with associated symptoms
  • ✓Imaging findings consistent with osteomyelitis
  • ✓Laboratory confirmation of infectious process
  • ✓Blood culture results when available
  • ✓Assessment of functional impairment and treatment response

Commonly Confused Codes

  • •M86.071/M86.072: Use when specific laterality is documented
  • •M86.179: Use for non-hematogenous acute osteomyelitis of unspecified ankle/foot
  • •M86.679: Use for chronic osteomyelitis of unspecified ankle/foot
  • •L03.116/L03.117: Use for cellulitis without bone involvement

Child Codes

M86.071Acute hematogenous osteomyelitis, right ankle and foot
HCC 92
M86.072Acute hematogenous osteomyelitis, left ankle and foot
HCC 92
M86.079Acute hematogenous osteomyelitis, unspecified ankle and foot
HCC 92

Code Hierarchy

└M86Osteomyelitis└M86.0Acute hematogenous osteomyelitis└M86.07Acute hematogenous osteomyelitis, ankle and foot└M86.079Acute hematogenous osteomyelitis, unspecified ankle and foot
└M86.079Acute hematogenous osteomyelitis, unspecified ankle and foot

Because M86.079 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.

M86.079 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 M86.079 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 M86.079 in HCC Buddy

Open M86.079 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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