Alphabetic Index FY2027

M86.9

Osteomyelitis, unspecified

FY2027Chapter 13: Diseases of the musculoskeletal system and connective tissue/M86–M90 Other osteopathies

BillableComplete code, valid to report
Care settingsHospital CCIPF Comorbidity · Severe Musculoskeletal & Connective Tissue Diseases

M86.9 (also written M869) is a billable ICD-10-CM diagnosis code for osteomyelitis, unspecified. It is part of the FY2027 code set, effective October 1, 2026. It is one of the 195 codes in category M86 (Osteomyelitis). The Alphabetic Index lists it under 1 entry. Its coding notes include a Use additional code instruction, 5 Excludes1 entries and 14 Excludes2 entries.

Use additional code

Add the listed code as a secondary code, if known.

Inherited from M86 Osteomyelitis
  • code (B95-B97) to identify infectious agent
  • code to identify major osseous defect, if applicable (M89.7-)

Excludes1

Not coded here. The listed conditions generally should not be reported together.

Inherited from M86 Osteomyelitis
Also from chapter/block level (1 note)
Inherited from M86–M90 Other osteopathies
  • postprocedural osteopathies (M96.-)

Excludes2

Not included here. Both codes may be reported if the patient has both conditions.

Inherited from M86 Osteomyelitis
Also from chapter/block level (10 notes)
Inherited from Chapter 13 Diseases of the musculoskeletal system and connective tissue
  • arthropathic psoriasis (L40.5-)
  • certain conditions originating in the perinatal period (P04-P96)
  • certain infectious and parasitic diseases (A00-B99)
  • compartment syndrome (traumatic) (T79.A-)
  • complications of pregnancy, childbirth and the puerperium (O00-O9A)
  • congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
  • endocrine, nutritional and metabolic diseases (E00-E88)
  • injury, poisoning and certain other consequences of external causes (S00-T88)
  • neoplasms (C00-D49)
  • symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)

Care settings

How CMS programs treat this code. These are CMS claim edits and list entries, not coverage or eligibility rules.

Hospital CC

Counts as a complication or comorbidity (CC) when reported as a secondary diagnosis on an inpatient claim. It does not count when the principal diagnosis is one of the 168 codes in its exclusion list. Some MS-DRGs also ignore a CC or MCC that defines the DRG.

Source: CMS MS-DRG Definitions Manual v44, effective October 1, 2026, Appendix C

IPF Comorbidity

On the CMS IPF comorbidity list.

Comorbidity categoryFactor
Severe Musculoskeletal & Connective Tissue Diseases1.05
It counts as a comorbidity when reported as a secondary diagnosis and actively treated during the stay. An IPF receives only one adjustment within a category and can receive adjustments in more than one category.

Source: CMS IPF PPS FY 2027 final rule (CMS-1847-F), Addendum B-3 (comorbidity codes with adjustment factor); effective for discharges on or after October 1, 2026

Inclusion terms

Conditions classified to this code.

This code
  • Infection of bone NOS
  • Periostitis without osteomyelitis

Notes

Also from chapter/block level (1 note)
Inherited from Chapter 13 Diseases of the musculoskeletal system and connective tissue
  • Use an external cause code following the code for the musculoskeletal condition, if applicable, to identify the cause of the musculoskeletal condition

Alphabetic Index terms

Terms the official Alphabetic Index lists for this code. 1 entry