2026 ICD-10-CM Diagnosis Code M86.9Osteomyelitis, unspecified

ICD-10-CM Codes›M00–M99›M86-M90›M86

ICD-10-CM M86.9
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M86.9 is a billable ICD-10-CM diagnosis code for osteomyelitis, unspecified. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 456 through 458, 539 through 541. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Osteomyelitis.

Code Identity

ICD-10-CM Code
M86.9
Billable Status
Yes — Valid for Submission
Code Describes
Osteomyelitis, unspecified
Short Description
Osteomyelitis, unspecified
Same as the full description in the CMS dataset.
Parent Code
M86
Osteomyelitis

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM86-M90Other osteopathies
CategoryM86Osteomyelitis
This CodeM86.9Osteomyelitis, unspecified

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Bacterial osteomyelitis
  • Bone abscess
  • Coccidioidomycosis of bone
  • Cranial cerebrospinal fluid leak
  • Enthesitis
  • Infection by Pasteurella multocida
  • Infection of bone
  • Infection of bone associated with bone plate
  • Infection of bone associated with bone screw
  • Infection of bone of ankle and/or foot
  • Infection of bone of hand
  • Infection of bone of radius and/or ulna
  • Infection of bone of tibia and/or fibula
  • Infection of calcaneum
  • Infection of carpal bone
  • Infection of femur
  • Infection of fibula
  • Infection of humerus
  • Infection of metacarpal
  • Infection of metatarsal
  • Infection of multiple bones
  • Infection of patella
  • Infection of pelvis
  • Infection of phalanx of finger or thumb
  • Infection of phalanx of toe
  • Infection of radius
  • Infection of scapula
  • Infection of talus
  • Infection of ulna
  • Leak of cranial cerebrospinal fluid due to osteomyelitis
  • Osteitis
  • Osteitis of hand
  • Osteitis of left femur
  • Osteitis of lower leg
  • Osteitis of multiple sites
  • Osteitis of pelvis
  • Osteitis of right femur
  • Osteitis of shoulder region
  • Osteomyelitis
  • Osteomyelitis caused by Staphylococcus aureus
  • Osteomyelitis due to type 1 diabetes mellitus
  • Osteomyelitis of ankle
  • Osteomyelitis of clavicle
  • Osteomyelitis of cranium
  • Osteomyelitis of facial bone
  • Osteomyelitis of forearm
  • Osteomyelitis of forefoot
  • Osteomyelitis of frontal bone
  • Osteomyelitis of hand
  • Osteomyelitis of hindfoot
  • Osteomyelitis of left ankle
  • Osteomyelitis of left femur
  • Osteomyelitis of left foot
  • Osteomyelitis of left hand
  • Osteomyelitis of left shoulder
  • Osteomyelitis of left tibia
  • Osteomyelitis of lower leg
  • Osteomyelitis of midfoot
  • Osteomyelitis of multiple sites
  • Osteomyelitis of pelvic region
  • Osteomyelitis of right ankle
  • Osteomyelitis of right femur
  • Osteomyelitis of right foot
  • Osteomyelitis of right hand
  • Osteomyelitis of right shoulder
  • Osteomyelitis of right tibia
  • Osteomyelitis of shoulder region
  • Osteomyelitis of sphenoid bone
  • Osteomyelitis of temporal bone
  • Osteomyelitis of tibia
  • Osteomyelitis of upper arm
  • Osteomyelitis of upper limb
  • Osteomyelitis of zygomatic bone
  • Pasteurella multocida osteomyelitis
  • Pedal osteitis
  • Periostitis
  • Periostitis of forearm
  • Periostitis of forearm without osteomyelitis
  • Periostitis of hand
  • Periostitis of hand without osteomyelitis
  • Periostitis without osteomyelitis
  • Periostitis without osteomyelitis of cervical spine
  • Periostitis without osteomyelitis of coccyx
  • Periostitis without osteomyelitis of lumbar spine
  • Periostitis without osteomyelitis of sacral vertebra
  • Periostitis without osteomyelitis of thoracic spine
  • SAPHO syndrome
  • Sternal osteomyelitis
  • Tenoperiostitis

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Infection of bone NOS
  • Periostitis without osteomyelitis

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Osteomyelitis(general) (infective) (localized) (neonatal) (purulent) (septic) (staphylococcal) (streptococcal) (suppurative) (with periostitis)

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR MUS002
Osteomyelitis
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Osteomyelitis

    inflammation of the bone as a result of infection. it may be caused by a variety of infectious agents, especially pyogenic (pus - producing) bacteria.

  • Dry Socket

    a condition sometimes occurring after tooth extraction, particularly after traumatic extraction, resulting in a dry appearance of the exposed bone in the socket, due to disintegration or loss of the blood clot. it is basically a focal osteomyelitis without suppuration and is accompanied by severe pain (alveolalgia) and foul odor. (dorland, 28th ed)

  • Fibrous Dysplasia of Bone

    a disease of bone marked by thinning of the cortex by fibrous tissue containing bony spicules, producing pain, disability, and gradually increasing deformity. only one bone may be involved (fibrous dysplasia, monostotic) or several (fibrous dysplasia, polyostotic).

  • Osteitis

    inflammation of the bone.

  • Osteitis Deformans

    a disease marked by repeated episodes of increased bone resorption followed by excessive attempts at repair, resulting in weakened, deformed bones of increased mass. the resultant architecture of the bone assumes a mosaic pattern in which the fibers take on a haphazard pattern instead of the normal parallel symmetry.

  • Osteitis Fibrosa Cystica

    a fibrous degeneration, cyst formation, and the presence of fibrous nodules in bone, usually due to hyperparathyroidism.

  • Periostitis

    inflammation of the periosteum. the condition is generally chronic, and is marked by tenderness and swelling of the bone and an aching pain. acute periostitis is due to infection, is characterized by diffuse suppuration, severe pain, and constitutional symptoms, and usually results in necrosis. (dorland, 27th ed)

  • Hyperparathyroidism

    a condition of abnormally elevated output of parathyroid hormone (or pth) triggering responses that increase blood calcium. it is characterized by hypercalcemia and bone resorption, eventually leading to bone diseases. primary hyperparathyroidism is caused by parathyroid hyperplasia or parathyroid neoplasms. secondary hyperparathyroidism is increased pth secretion in response to hypocalcemia, usually caused by chronic kidney diseases.

  • Enthesitis

    inflammation at the site of insertion of ligaments, tendons, and other fibrous structures into bone.

  • Enthesitis-Related Arthritis|ERA|ERA|Enthesitis-Related JIA|Enthesitis-Related JIA|Enthesitis-Related Juvenile Idiopathic Arthritis|Enthesitis-Related Juvenile Idiopathic Arthritis

    a category of juvenile idiopathic arthritis associated with arthritis and enthesitis, which may involve the axial skeleton. it is a form of juvenile spondyloarthritis.

Patient EducationClinical

Bone Infections

Like other parts of the body, bones can get infected. The infections are usually bacterial, but can also be fungal. They may spread to the bone from nearby skin or muscles, or from another part of the body through the bloodstream.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert M86.9 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
730.20 Osteomyelitis NOS-unspec
Approximate The match is approximate rather than exact.
ICD-9-CM
730.30 Periostitis-unspec
Approximate The match is approximate rather than exact.
ICD-9-CM
730.90 Bone infec NOS-unsp site
Approximate The match is approximate rather than exact.
ICD-9-CM
730.98 Bone infect NOS-oth site
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About M86.9Overview

Is M86.9 (Osteomyelitis) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report osteomyelitis, unspecified on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does M86.9 group to?

When osteomyelitis, unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 456, 457, 458, 539, 540, 541, with relative weights from 0.7715 to 8.4034 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of M86.9?

Under the General Equivalence Mappings, osteomyelitis, unspecified converts to ICD-9-CM 730.20 (osteomyelitis NOS-unspec), 730.30 (periostitis-unspec), and 730.90 (bone infec NOS-unsp site). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.