M86.161 ICD-10-CM Code: Other acute osteomyelitis, right tibia and fibula
HCC Buddy Code Card
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FY 2026 Apr update / Diseases of the musculoskeletal system and connective tissue (M00-M99) / Other osteopathies (M86-M90)
M86.161
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceOther acute osteomyelitis, right tibia and fibula
A rapidly developing bone infection affecting the right shinbone and smaller bone of the lower leg.
Buddy Insight
Acute osteomyelitis affecting both tibia and fibula of the right lower leg represents a complex dual-bone infection with significant implications for weight-bearing and ambulation.
CMS-HCC V28
MappedHCC 92
RAF 0.209
CMS-HCC V24
MappedHCC 39
RAF 0.482
ACA/HHS
00
RAF 0
ESRD/PACE
MappedHCC 39
RAF 0.0
RXHCC
00
RAF 0
Code Trumping
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Code Book Path
Inclusion Terms
OfficialICD-10-CM does not list inclusion terms for M86.161 in this effective period.
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for M86.161 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for M86.161 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for M86.161 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for M86.161 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for M86.161 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for M86.161 in this effective period.
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.
Is M86.161 an HCC code?
Yes. M86.161 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 M86.161
For M86.161to 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 M86.161 during that encounter, not just copy-forwarded from a problem list.
What This Code Means
M86.161 is the ICD-10-CM diagnosis code for other acute osteomyelitis, right tibia and fibula. A rapidly developing bone infection affecting the right shinbone and smaller bone of the lower leg. M86.161 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, M86.161 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, M86.161 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.
Ensure documentation clearly specifies right tibia and fibula involvement before assigning this code. Because M86.161 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 M86.161 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Ensure documentation clearly specifies right tibia and fibula involvement before assigning this code
- •Distinguish between acute, subacute, and chronic osteomyelitis as they have different code ranges
Clinical Significance
Acute osteomyelitis affecting both tibia and fibula of the right lower leg represents a complex dual-bone infection with significant implications for weight-bearing and ambulation. This condition requires aggressive treatment due to the critical role of these bones in lower extremity function.
Documentation Requirements
- ✓Specific documentation of right tibia and fibula involvement
- ✓Evidence of acute infection onset in lower leg bones
- ✓Clinical signs of dual bone infection
- ✓Imaging confirmation showing both tibia and fibula involvement
- ✓Laboratory evidence of active bone infection
- ✓Assessment of weight-bearing capacity
- ✓Documentation of functional impact on ambulation
- ✓Comprehensive treatment plan for dual bone involvement
Commonly Confused Codes
- •M86121 — Acute hematogenous osteomyelitis of right tibia and fibula
- •M86661 — Chronic osteomyelitis with draining sinus of right tibia and fibula
- •M86261 — Subacute osteomyelitis of right tibia and fibula
- •S82.90XA — Unspecified fracture of right lower leg
- •M25561 — Pain in right knee