2026 ICD-10-CM Diagnosis Code M00.861Arthritis due to other bacteria, right knee
ICD-10-CM Codes›M00–M99›M00-M02›M00
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Risk Adjusts — HCC 92
- Not Chronic
M00.861 is a billable ICD-10-CM diagnosis code for arthritis due to other bacteria, right knee. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 485 through 487, 548 through 550. 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 447 closely related codes. Coders also document this condition as arthritis of bilateral knee joints caused by bacteria. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Bacterial infections and Infective arthritis.
For Medicare Advantage risk adjustment, M00.861 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 2026.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
M00.861 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 2026.
Source: CMS Payment Year 2026 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.
- Arthritis of bilateral knee joints caused by bacteria
- Arthritis of left knee caused by bacteria
- Arthritis of right knee caused by bacteria
- Bilateral infective arthritis of knees
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Patient EducationClinical
Infectious Arthritis
Most kinds of arthritis cause pain and swelling in your joints. Joints are places where two bones meet, such as your elbow or knee. Infectious arthritis is an infection in the joint. The infection comes from a bacterial, viral, or fungal infection that spreads from another part of the body. Symptoms of infectious arthritis include:
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert M00.861 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About M00.861Overview
What is the ICD-10 code for arthritis due to other bacteria, right knee?
The ICD-10-CM code for arthritis due to other bacteria, right knee is M00.861 (sometimes written as M00861). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
Is M00.861 (Arthritis due to other bacteria, knee) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report arthritis due to other bacteria, right knee on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does M00.861 group to?
When arthritis due to other bacteria, right knee is the principal diagnosis on an inpatient stay, it groups to MS-DRG 485, 486, 487, 548, 549, 550, with relative weights from 0.8741 to 3.2271 depending on complications. Higher weights mean higher Medicare reimbursement.
Is M00.861 a CC or MCC?
CMS lists M00.861 as a CC (complication or comorbidity) for FY 2026. 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 447 closely related codes in its exclusion list.
What is the ICD-9 equivalent of M00.861?
Under the General Equivalence Mappings, arthritis due to other bacteria, right knee converts to ICD-9-CM 711.06 (pyogen arthritis-l/leg) and 041.89 (oth specf bacteria). The mapping is approximate, so confirm the match fits the documentation.
What HCC is M00.861?
M00.861 (arthritis due to other bacteria, right knee) 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 2026. 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. It does not map to any RxHCC in the Part D prescription drug model.
Does M00.861 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, M00.861 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.
