2026 ICD-10-CM Diagnosis Code M01.X42Direct infection of left hand in infectious and parasitic diseases classified elsewhere
ICD-10-CM Codes›M00–M99›M00-M02›M01
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Risk Adjusts — HCC 92
- Not Chronic
M01.X42 is a billable ICD-10-CM diagnosis code for direct infection of left hand in infectious and parasitic diseases classified elsewhere. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 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 938 closely related codes. The code is a manifestation code that cannot be reported as the principal diagnosis. Coders also document this condition as bilateral infective arthritis of hands. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Infective arthritis.
For Medicare Advantage risk adjustment, M01.X42 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
Code EditsBilling
Medicare Code Editor checks that affect claim validity for M01.X42.
Medicare Risk Adjustment (HCC)Billing
M01.X42 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 infective arthritis of hands
- Bilateral viral arthritis of joint of hands
- Infective arthritis of left hand
- Infective arthritis of right hand
- Viral arthritis of hand
- Viral arthritis of joint of left hand
- Viral arthritis of joint of right hand
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 M01.X42 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About M01.X42Overview
Is M01.X42 a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report direct infection of left hand in infectious and parasitic diseases classified elsewhere on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does M01.X42 group to?
On inpatient claims, direct infection of left hand in infectious and parasitic diseases classified elsewhere maps to MS-DRG 548, 549, 550, with relative weights from 0.8741 to 1.9309 depending on complications. Higher weights mean higher Medicare reimbursement.
Is M01.X42 a CC or MCC?
CMS lists M01.X42 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 938 closely related codes in its exclusion list.
Can M01.X42 be a principal diagnosis?
No. This is a manifestation code: direct infection of left hand in infectious and parasitic diseases classified elsewhere describes the manifestation of an underlying disease rather than the disease itself, so the underlying condition is sequenced first.
What is the ICD-9 equivalent of M01.X42?
Under the General Equivalence Mappings, direct infection of left hand in infectious and parasitic diseases classified elsewhere converts to ICD-9-CM 711.44 (bact arthritis-hand), 711.54 (viral arthritis-hand), and 711.64 (mycotic arthritis-hand). The mapping is approximate, so confirm the match fits the documentation.
What HCC is M01.X42?
M01.X42 (direct infection of left hand in infectious and parasitic diseases classified elsewhere) 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 M01.X42 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, M01.X42 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.
