What is ICD-10 code M87.336?

M87.336 is the ICD-10-CM diagnosis code for Other secondary osteonecrosis of unspecified ulna. Death of bone tissue in the forearm bone (ulna) caused by an underlying condition or injury when the specific side is not documented or applicable. M87.336 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. M87.336 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. M87.336 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. M87.336 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.

What is the V28 vs V24 difference for M87.336?

CMS phased in the V28 risk adjustment model over payment years 2024 (33%), 2025 (67%), and 2026 (100%), replacing V24. V28 consolidates HCC categories, removes some lower-acuity conditions, and recalibrates RAF weights across the entire model. For M87.336, V28 maps to Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis at RAF 0.479 while V24 mapped to Bone/Joint/Muscle Infections/Necrosis at RAF 0.401. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting M87.336?

Use this code only when laterality cannot be determined from documentation; attempt to clarify with provider if possible This is a less specific code; bilateral involvement would require separate codes for each side Because M87.336 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.

2026 ICD-10-CM M87.336: Other secondary

ICD-10-CM Code View

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Code lookupM87.336Effective 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)

M87.336

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

Other secondary osteonecrosis of unspecified ulna

Death of bone tissue in the forearm bone (ulna) caused by an underlying condition or injury when the specific side is not documented or applicable.

Buddy Insight

Unspecified ulna secondary osteonecrosis represents bone death from identifiable non-traumatic causes when laterality cannot be determined.

CMS-HCC V28

Mapped

HCC 92

Bone/Joint/Muscle/Severe Soft...

RAF 0.479

CMS-HCC V24

Mapped

HCC 39

Bone/Joint/Muscle Infections/...

RAF 0.401

ACA/HHS

Mapped

HCC 55

HHS-HCC 55

Varies by metal level

ESRD/PACE

Mapped

HCC 39

Bone/Joint/Muscle Infections/...

RAF 0.092

RXHCC

Mapped

HCC 80

Bone/Joint/Muscle Infections/...

RAF 0.204

Code Book Path

Official

M87.3Other secondary osteonecrosis

M87.33Other secondary osteonecrosis of radius, ulna and carpus

M87.336Other secondary osteonecrosis of unspecified ulna

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for M87.336 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for M87.336 in this effective period.

Related Child Codes

Official

M87.331Other secondary osteonecrosis of right radius

M87.332Other secondary osteonecrosis of left radius

M87.333Other secondary osteonecrosis of unspecified radius

M87.334Other secondary osteonecrosis of right ulna

M87.335Other secondary osteonecrosis of left ulna

Includes

Official

ICD-10-CM does not list Includes notes for M87.336 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for M87.336 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for M87.336 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for M87.336 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for M87.336 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Documentation of underlying secondary cause of osteonecrosis

Imaging evidence of ulnar osteonecrosis without specified side

Clinical findings consistent with ulnar dysfunction

Documentation explaining why laterality is unspecified

MEAT Support

HCC Buddy guidance

Documentation of underlying secondary cause of osteonecrosis

Imaging evidence of ulnar osteonecrosis without specified side

Clinical findings consistent with ulnar dysfunction

Documentation explaining why laterality is unspecified

Audit Caution

HCC Buddy guidance

Using more specific laterality when side is unknown

Missing documentation of secondary causative factors

Using when laterality could be determined from documentation

Confusing with idiopathic or traumatic forms

Common Mistakes

HCC Buddy guidance

M87.036 — Idiopathic osteonecrosis of unspecified ulna (no secondary cause)

M87.236 — Osteonecrosis due to previous trauma of unspecified ulna (traumatic)

S52.609A — Unspecified fracture of lower end of unspecified ulna (acute)

M86.039 — Acute hematogenous osteomyelitis of unspecified ulna (infection)

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 M87.336 an HCC code?

Yes. M87.336 (Other secondary osteonecrosis of unspecified ulna) 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: M87.336 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: M87.336
Description: Other secondary osteonecrosis of unspecified ulna
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

RxHCCHCC 80, Bone/Joint/Muscle Infections/Necrosis

0.204

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 M87.336 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for M87.336

For M87.336 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 M87.336 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

M87.336 is the ICD-10-CM diagnosis code for other secondary osteonecrosis of unspecified ulna. Death of bone tissue in the forearm bone (ulna) caused by an underlying condition or injury when the specific side is not documented or applicable. M87.336 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, M87.336 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, M87.336 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; attempt to clarify with provider if possible. Because M87.336 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 M87.336 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; attempt to clarify with provider if possible
•This is a less specific code; bilateral involvement would require separate codes for each side

Clinical Significance

Unspecified ulna secondary osteonecrosis represents bone death from identifiable non-traumatic causes when laterality cannot be determined. This condition affects forearm stability and requires comprehensive management addressing both the underlying cause and bone pathology.