2026 ICD-10-CM Diagnosis Code M00.9Pyogenic arthritis, unspecified
ICD-10-CM Codes›M00–M99›M00-M02›M00
- Billable — Valid for Submission
- CC — Complication or Comorbidity
- Risk Adjusts — HCC 92
- Not Chronic
M00.9 is a billable ICD-10-CM diagnosis code for pyogenic arthritis, unspecified. 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 938 closely related codes. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Bacterial infections and Infective arthritis.
For Medicare Advantage risk adjustment, M00.9 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
M00.9 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.
- Acute bacterial arthritis
- Acute infective arthritis
- Acute infective polyarthritis
- Acute polyarthritis
- Acute suppurative arthritis
- Acute suppurative arthritis caused by bacteria
- Arthritis due to parasitic infection
- Arthritis of lower limb due to parasitic infection
- Arthritis of temporomandibular joint caused by internal joint prosthesis
- Bilateral infective arthritis of hands
- Bilateral infective arthritis of hips
- Bilateral infective arthritis of knees
- Bilateral infective arthritis of wrist regions
- Chronic infective arthritis
- Chronic infective polyarthritis
- Cystic acne
- Elbow pyogenic arthritis
- Hidradenitis suppurativa pyoderma gangrenosum complex
- Infectious arthritis of temporomandibular joint
- Infectious arthritis of temporomandibular joint caused by internal joint prosthesis
- Infectious disorder of joint
- Infective arthritis
- Infective arthritis co-occurrent with human immunodeficiency virus infection
- Infective arthritis of ankle and/or foot
- Infective arthritis of distal interphalangeal joint of finger
- Infective arthritis of elbow
- Infective arthritis of first metatarsophalangeal joint
- Infective arthritis of hip
- Infective arthritis of interphalangeal joint of toe
- Infective arthritis of joint of bilateral shoulder regions
- Infective arthritis of joint of hand
- Infective arthritis of joint of left shoulder region
- Infective arthritis of joint of right shoulder region
- Infective arthritis of left ankle
- Infective arthritis of left elbow
- Infective arthritis of left foot
- Infective arthritis of left glenohumeral joint
- Infective arthritis of left hand
- Infective arthritis of left hip
- Infective arthritis of left knee
- Infective arthritis of left wrist
- Infective arthritis of metatarsophalangeal joint of lesser toe
- Infective arthritis of pelvis
- Infective arthritis of proximal interphalangeal joint of finger
- Infective arthritis of right ankle
- Infective arthritis of right elbow
- Infective arthritis of right foot
- Infective arthritis of right glenohumeral joint
- Infective arthritis of right hand
- Infective arthritis of right hip
- Infective arthritis of right knee
- Infective arthritis of right wrist
- Infective arthritis of shoulder region
- Infective arthritis of wrist
- Infective arthritis with AIDS
- Infective polyarthritis
- Inflammation of interphalangeal joint of toe
- Knee pyogenic arthritis
- PAPASH syndrome
- Polyarticular viral arthritis
- Pyogenic arthritis of foot
- Pyogenic arthritis of hip
- Pyogenic arthritis of multiple sites
- Pyogenic arthritis of pelvic region
- Pyogenic arthritis of shoulder region
- Pyogenic arthritis of the ankle and/or foot
- Pyogenic arthritis of the pelvic region and thigh
- Pyogenic arthritis, pyoderma gangrenosum, acne syndrome
- Subacute arthritis
- Subacute arthropathy
- Subacute infective arthritis
- Subacute infective polyarthritis
- Suppurative arthritis
- Suppurative arthritis caused by bacteria
- Viral arthritis
- Wrist pyogenic arthritis
Tabular List NotesGuidance
Coding notes and annotation back-references applicable to this code.
Inclusion Terms
- Infective arthritis NOS
These terms are the conditions for which that code is to be used. The terms may be synonyms of the code title, or, in the case of "other specified" codes, the terms are a list of the various conditions assigned to that code. The inclusion terms are not necessarily exhaustive. Additional terms found only in the Alphabetic Index may also be assigned to a code.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Abscess (connective tissue) (embolic) (fistulous) (infective) (metastatic) (multiple) (pernicious) (pyogenic) (septic) L02.91
Disease, diseased See Also: Syndrome;
suppurative M00.9
Infection, infected, infective (opportunistic) B99.9
acromioclavicular M00.9
hip (joint) NEC M00.9
joint NEC M00.9
knee (joint) NEC M00.9
joint M00.9
metatarsophalangeal M00.9
shoulder (joint) NEC M00.9
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 M00.9 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About M00.9Overview
What is the ICD-10 code for pyogenic arthritis, unspecified?
The ICD-10-CM code for pyogenic arthritis, unspecified is M00.9 (sometimes written as M009). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
Is M00.9 (Pyogenic arthritis) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report pyogenic arthritis, unspecified on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does M00.9 group to?
When pyogenic arthritis, unspecified 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 M00.9 a CC or MCC?
CMS lists M00.9 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.
What is the ICD-9 equivalent of M00.9?
Under the General Equivalence Mappings, pyogenic arthritis, unspecified converts to ICD-9-CM 711.00 (pyogen arthritis-unspec). The mapping is approximate, so confirm the match fits the documentation.
What HCC is M00.9?
M00.9 (pyogenic arthritis, unspecified) 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 M00.9 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, M00.9 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.
