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M90.531 ICD-10-CM Code: Osteonecrosis in diseases classified elsewhere, right forearm

M90.531 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)

M90.531

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

Osteonecrosis in diseases classified elsewhere, right forearm

Death of bone tissue in the right forearm caused by another disease or condition affecting the body.

Buddy the Bee presenting code insight

Buddy Insight

Secondary osteonecrosis of the right forearm represents bone death in the radius and/or ulna caused by underlying systemic disease, potentially affecting hand and wrist function.

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

HCC 80

RAF 0.204

Code Book Path

Official
M90.5Osteonecrosis in diseases classified elsewhere
M90.53Osteonecrosis in diseases classified elsewhere, forearm
M90.531Osteonecrosis in diseases classified elsewhere, right forearm

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for M90.531 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for M90.531 in this effective period.

Related Child Codes

Official
M90.532Osteonecrosis in diseases classified elsewhere, left forearm
M90.539Osteonecrosis in diseases classified elsewhere, unspecified forearm

Includes

Official

ICD-10-CM does not list Includes notes for M90.531 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for M90.531 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for M90.531 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for M90.531 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for M90.531 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance
Underlying causative disease documented and coded first
Right forearm (radius/ulna) specifically identified as affected site
Clinical evidence of bone tissue death present
Imaging studies confirming forearm osteonecrosis

MEAT Support

HCC Buddy guidance
Underlying causative disease documented and coded first
Right forearm (radius/ulna) specifically identified as affected site
Clinical evidence of bone tissue death present
Imaging studies confirming forearm osteonecrosis

Audit Caution

HCC Buddy guidance
Not coding the underlying disease that caused the osteonecrosis
Confusing right and left forearm laterality
Using primary osteonecrosis codes when secondary etiology is present
Coding only fracture complications without addressing underlying necrosis

Common Mistakes

HCC Buddy guidance
M87.031 — Idiopathic aseptic necrosis of right radius (primary osteonecrosis)
M90.532 — Osteonecrosis in diseases classified elsewhere, left forearm (wrong laterality)
M90.539 — Osteonecrosis in diseases classified elsewhere, unspecified forearm (lacks laterality)
M84.431 — Pathological fracture, right radius (fracture complication, not necrosis)

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 M90.531 an HCC code?

Yes. M90.531 (Osteonecrosis in diseases classified elsewhere, right forearm) 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: M90.531 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
M90.531
Description
Osteonecrosis in diseases classified elsewhere, right forearm
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 M90.531 in the Code Book — tabular path, V28 RAF, and MEAT checklist →

MEAT Criteria for M90.531

For M90.531 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 M90.531 during that encounter, not just copy-forwarded from a problem list.

Coder workflow notes

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What This Code Means

M90.531 is the ICD-10-CM diagnosis code for osteonecrosis in diseases classified elsewhere, right forearm. Death of bone tissue in the right forearm caused by another disease or condition affecting the body. M90.531 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, M90.531 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, M90.531 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.

Forearm includes the radius and ulna bones; confirm the underlying etiology is documented. Because M90.531 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 M90.531 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

  • •Forearm includes the radius and ulna bones; confirm the underlying etiology is documented
  • •This is a secondary code - the primary diagnosis should be the disease causing the osteonecrosis

Clinical Significance

Secondary osteonecrosis of the right forearm represents bone death in the radius and/or ulna caused by underlying systemic disease, potentially affecting hand and wrist function. This condition requires management of both the primary disease and skeletal complications to prevent further deterioration.

Documentation Requirements

  • ✓Underlying causative disease documented and coded first
  • ✓Right forearm (radius/ulna) specifically identified as affected site
  • ✓Clinical evidence of bone tissue death present
  • ✓Imaging studies confirming forearm osteonecrosis
  • ✓Assessment of right arm and hand function
  • ✓Treatment plan for primary condition and bone complications
  • ✓Documentation of any associated wrist or elbow involvement

Commonly Confused Codes

  • •M87.031: Idiopathic aseptic necrosis of right radius (primary osteonecrosis)
  • •M90.532: Osteonecrosis in diseases classified elsewhere, left forearm (wrong laterality)
  • •M90.539: Osteonecrosis in diseases classified elsewhere, unspecified forearm (lacks laterality)
  • •M84.431: Pathological fracture, right radius (fracture complication, not necrosis)

Child Codes

M90.531Osteonecrosis in diseases classified elsewhere, right forearm
HCC 92
M90.532Osteonecrosis in diseases classified elsewhere, left forearm
HCC 92
M90.539Osteonecrosis in diseases classified elsewhere, unspecified forearm
HCC 92

Code Hierarchy

└M90Osteopathies in diseases classified elsewhere└M90.5Osteonecrosis in diseases classified elsewhere└M90.53Osteonecrosis in diseases classified elsewhere, forearm└M90.531Osteonecrosis in diseases classified elsewhere, right forearm
└M90.531Osteonecrosis in diseases classified elsewhere, right forearm

Because M90.531 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.

M90.531 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 M90.531 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.

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