M90.521 Osteonecrosis in diseases classified elsewhere, right upper arm

Billable ICD-10-CM code, FY2026. Acts as a Complication or Comorbidity (CC) as a secondary diagnosis.

Applies from M90 Osteopathies in diseases classified elsewhere

Excludes1 (never code together)

• osteochondritis, osteomyelitis, and osteopathy (in):
• cryptococcosis (B45.3)
• diabetes mellitus (E08-E13 with .69-)
• gonococcal (A54.43)
• neurogenic syphilis (A52.11)
• renal osteodystrophy (N25.0)
• salmonellosis (A02.24)
• secondary syphilis (A51.46)
• syphilis (late) (A52.77)

Applies from M90.5 Osteonecrosis in diseases classified elsewhere

Code first

• underlying disease, such as:
• caisson disease (T70.3)
• hemoglobinopathy (D50-D64)

Risk adjustment (HCC)

• CMS-HCC V28: HCC 92 — Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis
• CMS-HCC V22: HCC 39 — Bone/Joint/Muscle Infections/Necrosis
• RxHCC V08: HCC 80 — Aseptic Necrosis of Bone
• ESRD V24: HCC 39

MS-DRG index

Defines the logic of DRG(s) 553-554 in MDC 08.

Approximate ICD-9-CM (GEMs)

• 731.8 Other bone involvement in diseases classified elsewhere (approximate)
• 733.49 Aseptic necrosis of bone, other (approximate)

Medicare Code Edits (MCE v43.1 (April 2026))

• Manifestation codes as principal diagnosis: Manifestation codes describe the manifestation of an underlying disease, not the disease itself, and are not allowed as principal diagnosis.

Code annotations containing back-references to M90.521

Back-references to M90

• Type 1 Excludes: M87 Osteonecrosis ("osteochondropathies (M90-M93)")

Nearby codes

• M90.51 Osteonecrosis in diseases classified elsewhere, shoulder
• M90.511 Osteonecrosis in diseases classified elsewhere, right shoulder
• M90.512 Osteonecrosis in diseases classified elsewhere, left shoulder
• M90.519 Osteonecrosis in diseases classified elsewhere, unspecified shoulder
• M90.52 Osteonecrosis in diseases classified elsewhere, upper arm
• M90.521 Osteonecrosis in diseases classified elsewhere, right upper arm (this code)
• M90.522 Osteonecrosis in diseases classified elsewhere, left upper arm
• M90.529 Osteonecrosis in diseases classified elsewhere, unspecified upper arm
• M90.53 Osteonecrosis in diseases classified elsewhere, forearm
• M90.531 Osteonecrosis in diseases classified elsewhere, right forearm
• M90.532 Osteonecrosis in diseases classified elsewhere, left forearm