2027 ICD-10-CM Diagnosis Code M90.559Osteonecrosis in diseases classified elsewhere, unspecified thigh
ICD-10-CM Codes›M00–M99›M86-M90›M90
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Risk Adjusts — HCC 92
- Not Chronic
M90.559 is a billable ICD-10-CM diagnosis code for osteonecrosis in diseases classified elsewhere, unspecified thigh. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 553 through 554. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 184 closely related codes. The code is a manifestation code that cannot be reported as the principal diagnosis and flagged as an unspecified code, since codes identifying laterality exist in the same family. Coders also document this condition as osteonecrosis due to hemoglobinopathy. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Aseptic necrosis and osteonecrosis.
For Medicare Advantage risk adjustment, M90.559 maps to CMS-HCC Category 92 (Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis) under the V28 model, adding a risk factor of about 0.479 for a community, non-dual, aged beneficiary in payment year 2027.
Code Identity
Code Classification
Code EditsBilling
Medicare Code Editor checks that affect claim validity for M90.559.
Medicare Risk Adjustment (HCC)Billing
M90.559 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2027.
Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Osteonecrosis due to hemoglobinopathy
- Osteonecrosis of femur due to hemoglobinopathy
- Osteonecrosis of pelvic region due to hemoglobinopathy
- Osteonecrosis of pelvis
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to M90.559: its own notes plus those printed at M90.5, M90, block M86-M90, and Chapter 13. A note printed at a category, block or chapter applies to every code under it.
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
- postprocedural osteopathies (M96.-)
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
- 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)
Code First
The underlying condition named in the note is sequenced before this code.
Notes
General instructions on how these codes are used.
- Use an external cause code following the code for the musculoskeletal condition, if applicable, to identify the cause of the musculoskeletal condition
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Patient EducationClinical
Osteonecrosis
Osteonecrosis is a disease caused by reduced blood flow to bones in the joints. In people with healthy bones, new bone is always replacing old bone. In osteonecrosis, the lack of blood causes the bone to break down faster than the body can make enough new bone. The bone starts to die and may break down.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert M90.559 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About M90.559Overview
What is the ICD-10 code for osteonecrosis in diseases classified elsewhere, unspecified thigh?
The ICD-10-CM code for osteonecrosis in diseases classified elsewhere, unspecified thigh is M90.559 (sometimes written as M90559). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is M90.559 (Osteonecrosis in diseases classified elsewhere, thigh) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report osteonecrosis in diseases classified elsewhere, unspecified thigh on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does M90.559 group to?
On inpatient claims, osteonecrosis in diseases classified elsewhere, unspecified thigh maps to MS-DRG 554, 553, with relative weights from 0.8328 to 1.2492 depending on complications. Higher weights mean higher Medicare reimbursement.
Is M90.559 a CC or MCC?
CMS lists M90.559 as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 184 closely related codes in its exclusion list.
Can M90.559 be a principal diagnosis?
No. This is a manifestation code: osteonecrosis in diseases classified elsewhere, unspecified thigh describes the manifestation of an underlying disease rather than the disease itself, so the underlying condition is sequenced first.
What HCC is M90.559?
M90.559 (osteonecrosis in diseases classified elsewhere, unspecified thigh) maps to CMS-HCC Category 92 (Bone/Joint/Muscle/Severe Soft Tissue Infections/Necrosis), commonly written as HCC 92, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 39 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 80.
Does M90.559 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, M90.559 adds a risk adjustment factor of about 0.479 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.471 to 0.632 depending on the payment segment). HCC 92 sits at the top of its hierarchy, so no other condition category supersedes it. See the full factor table on the HCC 92 category page.
