What is ICD-10 code M86.561?

M86.561 is the ICD-10-CM diagnosis code for Other chronic hematogenous osteomyelitis, right tibia and fibula. A chronic bone infection of the right shinbone and smaller leg bone (tibia and fibula) that developed from bacteria spreading through the bloodstream. M86.561 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. M86.561 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. M86.561 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. M86.561 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

Which HCC does M86.561 map to under V28?

M86.561 maps to CMS-HCC V28 HCC 92 (Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis). The category numbers, labels, and conditions come from the CMS-HCC V28 model file for payment year 2026.

2026 ICD-10-CM M86.561: Other chronic hematogenous

M86.561 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

ICD-10-CM Code View

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Code lookupM86.561Effective periodFY2026 Apr Update (Apr 1-Sep 30)

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

M86.561

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

Other chronic hematogenous osteomyelitis, right tibia and fibula

A chronic bone infection of the right shinbone and smaller leg bone (tibia and fibula) that developed from bacteria spreading through the bloodstream.

Buddy Insight

Chronic hematogenous osteomyelitis affecting the right tibia and fibula represents a complex bone infection involving the primary weight-bearing bones of the lower leg.

CMS-HCC V28

Mapped

HCC 92

Bone/Joint/Muscle/Severe Soft...

Code-level coefficient reference

CMS-HCC V24

Historical

Not used for standard CY2026 Medicare Advantage payment. Select a historical period to review V24.

Not used for CY2026 payment

ACA/HHS

Mapped

HCC 055

HHS-HCC 055 adult, RAF varies...

Code-level coefficient reference

ESRD/PACE

Mapped

HCC 39

Bone/Joint/Muscle Infections/...

Code-level coefficient reference

RXHCC

N/A

—

Not risk-adjusted for this model/period.

Not mapped

Code Book Path

Official

M86.5Other chronic hematogenous osteomyelitis

M86.56Other chronic hematogenous osteomyelitis, tibia and fibula

M86.561Other chronic hematogenous osteomyelitis, right tibia and fibula

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for M86.561 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for M86.561 in this effective period.

Related Child Codes

Official

M86.562Other chronic hematogenous osteomyelitis, left tibia and fibula

M86.569Other chronic hematogenous osteomyelitis, unspecified tibia and fibula

Includes

Official

ICD-10-CM does not list Includes notes for M86.561 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for M86.561 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for M86.561 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for M86.561 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for M86.561 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Documentation of chronic nature (>6 weeks duration or recurrent)

Evidence of hematogenous origin (bloodstream spread)

Specific involvement of right tibia and/or fibula

Imaging studies showing bone infection (plain films, MRI, bone scan)

MEAT Support

HCC Buddy guidance

Documentation of chronic nature (>6 weeks duration or recurrent)

Evidence of hematogenous origin (bloodstream spread)

Specific involvement of right tibia and/or fibula

Imaging studies showing bone infection (plain films, MRI, bone scan)

Audit Caution

HCC Buddy guidance

Distinguishing from post-traumatic osteomyelitis which has different coding

Confusion with stress fractures or other bone pathology in athletes

Missing the hematogenous component when etiology is not clearly documented

Using acute codes during exacerbations of chronic condition

Common Mistakes

HCC Buddy guidance

M86.562 — Other chronic hematogenous osteomyelitis, left tibia and fibula (opposite side)

M86.661 — Other chronic osteomyelitis, right tibia and fibula (non-hematogenous)

M86.461 — Chronic osteomyelitis with draining sinus, right tibia and fibula (has sinus)

M86.161 — Other acute osteomyelitis, right tibia and fibula (acute phase)

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 M86.561 an HCC code?

Yes. M86.561 (Other chronic hematogenous osteomyelitis, right tibia and fibula) 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: M86.561 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: M86.561
Description: Other chronic hematogenous osteomyelitis, right tibia and fibula
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 M86.561 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →

MEAT Criteria for M86.561

For M86.561 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 M86.561 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

M86.561 is the ICD-10-CM diagnosis code for other chronic hematogenous osteomyelitis, right tibia and fibula. A chronic bone infection of the right shinbone and smaller leg bone (tibia and fibula) that developed from bacteria spreading through the bloodstream. M86.561 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, M86.561 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 M86.561; 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.

This code covers both the tibia and fibula on the right side; do not assign separate codes for each bone. Because M86.561 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 M86.561 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•This code covers both the tibia and fibula on the right side; do not assign separate codes for each bone
•Confirm right leg is documented to avoid miscoding as left or unspecified

Clinical Significance

Chronic hematogenous osteomyelitis affecting the right tibia and fibula represents a complex bone infection involving the primary weight-bearing bones of the lower leg. This condition significantly impacts mobility and may lead to long-term disability, requiring coordinated medical and surgical management.

Documentation Requirements

✓Documentation of chronic nature (>6 weeks duration or recurrent)
✓Evidence of hematogenous origin (bloodstream spread)
✓Specific involvement of right tibia and/or fibula
✓Imaging studies showing bone infection (plain films, MRI, bone scan)
✓Laboratory evidence of infection (ESR, CRP, cultures)
✓Assessment of lower extremity function and weight-bearing ability
✓Documentation of treatment regimen and surgical interventions
✓Evaluation for complications such as fractures or deformity

Commonly Confused Codes

•M86.562: Other chronic hematogenous osteomyelitis, left tibia and fibula (opposite side)
•M86.661: Other chronic osteomyelitis, right tibia and fibula (non-hematogenous)
•M86.461: Chronic osteomyelitis with draining sinus, right tibia and fibula (has sinus)
•M86.161: Other acute osteomyelitis, right tibia and fibula (acute phase)
•S82.90XA: Unspecified fracture of right lower leg (trauma-related)