2026 ICD-10-CM Diagnosis Code M05.861Other rheumatoid arthritis with rheumatoid factor of right knee
ICD-10-CM Codes›M00–M99›M05-M14›M05
- Billable — Valid for Submission
- Risk Adjusts — HCC 93
- Chronic Condition
M05.861 is a billable ICD-10-CM diagnosis code for other rheumatoid arthritis with rheumatoid factor of right knee. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 545 through 547. Coders also document this condition as bilateral rheumatoid arthritis of knees. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Rheumatoid arthritis and related disease.
For Medicare Advantage risk adjustment, M05.861 maps to CMS-HCC Category 93 (Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders) under the V28 model, adding a risk factor of about 0.617 for a community, non-dual, aged beneficiary in payment year 2026.
This medical diagnosis code is frequently used in Orthopedics medical specialties to designate conditions such rheumatoid arthritis.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
M05.861 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.
- Bilateral rheumatoid arthritis of knees
- Bilateral seropositive rheumatoid arthritis of knees
- Rheumatoid arthritis of knee
- Rheumatoid arthritis of left knee
- Rheumatoid arthritis of right knee
- Seropositive rheumatoid arthritis of right knee
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Patient EducationClinical
Rheumatoid Arthritis
Rheumatoid arthritis (RA) is a form of arthritis that causes pain, swelling, and stiffness in your joints. RA is an autoimmune disease. Although it is most common in the wrist and fingers, this disease can cause your immune system to attack any joint tissue. The inflammation (swelling) that comes with RA can also affect other body parts.
The full article covers:
- What is rheumatoid arthritis?
- Who is more likely to get rheumatoid arthritis?
- What causes rheumatoid arthritis?
- What are the symptoms of rheumatoid arthritis?
- How is rheumatoid arthritis diagnosed?
- What are the treatments for rheumatoid arthritis?
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert M05.861 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About M05.861Overview
What is the ICD-10 code for other rheumatoid arthritis with rheumatoid factor of right knee?
The ICD-10-CM code for other rheumatoid arthritis with rheumatoid factor of right knee is M05.861 (sometimes written as M05861). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
Is M05.861 (Other rheumatoid arthritis with rheumatoid factor of knee) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report other rheumatoid arthritis with rheumatoid factor of right knee on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does M05.861 group to?
When other rheumatoid arthritis with rheumatoid factor of right knee is the principal diagnosis on an inpatient stay, it groups to MS-DRG 545, 546, 547, with relative weights from 0.8362 to 2.4817 depending on complications. Higher weights mean higher Medicare reimbursement.
What is the ICD-9 equivalent of M05.861?
Under the General Equivalence Mappings, other rheumatoid arthritis with rheumatoid factor of right knee converts to ICD-9-CM 714.0 (rheumatoid arthritis). The mapping is approximate, so confirm the match fits the documentation.
What HCC is M05.861?
M05.861 (other rheumatoid arthritis with rheumatoid factor of right knee) maps to CMS-HCC Category 93 (Rheumatoid Arthritis and Other Specified Inflammatory Rheumatic Disorders), commonly written as HCC 93, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2026. It mapped to HCC 40 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 83.
Does M05.861 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, M05.861 adds a risk adjustment factor of about 0.617 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.288 to 0.617 depending on the payment segment). HCC 93 sits at the top of its hierarchy, so no other condition category supersedes it. See the full factor table on the HCC 93 category page.
