What is ICD-10 code M00.012?

M00.012 is the ICD-10-CM diagnosis code for Staphylococcal arthritis, left shoulder. A bacterial infection of the left shoulder joint caused by Staphylococcus bacteria. It belongs to the ICD-10-CM chapter for diseases of the musculoskeletal system and connective tissue (m00-m99). M00.012 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. M00.012 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. M00.012 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. M00.012 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

What is the V28 vs V24 difference for M00.012?

CMS phased in the V28 risk adjustment model over payment years 2024 (33%), 2025 (67%), and 2026 (100%), replacing V24. V28 consolidates HCC categories, removes some lower-acuity conditions, and recalibrates RAF weights across the entire model. For M00.012, V28 maps to Bone/Joint/Muscle Infections/Necrosis at RAF 0.209 while V24 mapped to Bone/Joint/Muscle Infections/Necrosis at RAF 0.482. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting M00.012?

Confirm left shoulder is documented as the infection site Differentiate from right shoulder (M00.011) and unspecified shoulder (M00.019) codes Because M00.012 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score.

M00.012 ICD-10 Code: Staphylococcal arthritis,

ICD-10-CM Code View

HCC Buddy Code Card

Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.

Code lookupM00.012Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the musculoskeletal system and connective tissue (M00-M99) / Infectious arthropathies (M00-M02)

M00.012

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Staphylococcal arthritis, left shoulder

A bacterial infection of the left shoulder joint caused by Staphylococcus bacteria.

Buddy Insight

Staphylococcal arthritis of the left shoulder is a serious bacterial joint infection (septic arthritis) requiring emergency treatment to prevent permanent joint damage.

CMS-HCC V28

Mapped

HCC 92

Bone/Joint/Muscle Infections/...

RAF 0.209

CMS-HCC V24

Mapped

HCC 39

Bone/Joint/Muscle Infections/...

RAF 0.482

ACA/HHS

Not risk-adjusted for this model/period.

RAF 0

ESRD/PACE

Mapped

HCC 39

Bone/Joint/Muscle Infections/...

RAF 0.0

RXHCC

Not risk-adjusted for this model/period.

RAF 0

Code Trumping

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Compare selected patient codes to show trumped or trumps impact.

Code Book Path

Official

M00.0Staphylococcal arthritis and polyarthritis

M00.01Staphylococcal arthritis, shoulder

M00.012Staphylococcal arthritis, left shoulder

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for M00.012 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for M00.012 in this effective period.

Related Child Codes

Official

M00.011Staphylococcal arthritis, right shoulder

M00.019Staphylococcal arthritis, unspecified shoulder

Includes

Official

ICD-10-CM does not list Includes notes for M00.012 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for M00.012 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for M00.012 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for M00.012 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for M00.012 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Provider documentation identifying Staphylococcus as the causative organism (culture results, clinical diagnosis, or documented species)

Documentation of the affected joint with specific anatomical site

Laterality documented as left side

Clinical findings supporting joint infection (joint effusion, warmth, erythema, limited range of motion, fever)

MEAT Support

HCC Buddy guidance

Provider documentation identifying Staphylococcus as the causative organism (culture results, clinical diagnosis, or documented species)

Documentation of the affected joint with specific anatomical site

Laterality documented as left side

Clinical findings supporting joint infection (joint effusion, warmth, erythema, limited range of motion, fever)

Audit Caution

HCC Buddy guidance

Coding staphylococcal arthritis without confirmed Staphylococcus identification — if organism is unknown, use M00.9 (pyogenic arthritis, unspecified) instead

Failing to differentiate between Staphylococcus aureus and other Staphylococcus species when documentation is available — M00.0x covers all Staphylococcus species

Not coding associated conditions such as sepsis (A41.0x for Staphylococcal sepsis) or osteomyelitis when documented alongside the septic arthritis

Coding a single joint code when multiple joints are infected — use M00.09 (polyarthritis) when more than one joint is involved

Common Mistakes

HCC Buddy guidance

M00.11x — Pneumococcal arthritis of same joint site; differs by causative organism (Pneumococcus vs. Staphylococcus)

M00.21x — Streptococcal arthritis of same joint site; differs by causative organism (Streptococcus vs. Staphylococcus)

M00.81x — Arthritis due to other bacteria at same joint site; use when organism is identified but not Staphylococcus

M00.9 — Pyogenic arthritis, unspecified; use only when causative organism cannot be identified

Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.

Is M00.012 an HCC code?

Yes. M00.012 maps to Bone/Joint/Muscle Infections/Necrosis under the CMS-HCC V28 risk adjustment model (and Bone/Joint/Muscle Infections/Necrosis under V24).

HCC Category Mapping

V28HCC 92 — Bone/Joint/Muscle Infections/Necrosis

0.209

V24HCC 39 — Bone/Joint/Muscle Infections/Necrosis

0.482

ESRDHCC 39 — Bone/Joint/Muscle Infections/Necrosis

0.000

RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.

MEAT Criteria for M00.012

For M00.012to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically — it has to be re-documented and supported each calendar year.

MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
EEvaluate: test results, medication response, or physical findings reviewed by the provider
AAssess: explicit mention in the assessment or plan with acknowledgment of status
TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis

Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed M00.012 during that encounter — not just copy-forwarded from a problem list.

What This Code Means

M00.012 is the ICD-10-CM diagnosis code for staphylococcal arthritis, left shoulder. A bacterial infection of the left shoulder joint caused by Staphylococcus bacteria. M00.012 sits in the ICD-10-CM chapter for diseases of the musculoskeletal system and connective tissue (m00-m99), within the section covering infectious arthropathies (m00-m02).

Under the CMS-HCC V28 risk adjustment model, M00.012 maps to Bone/Joint/Muscle Infections/Necrosis (HCC 92) with a community, non-dual, aged base RAF weight of 0.209. Under the older V24 model, M00.012 mapped to the same category but with a base RAF weight of 0.482 — V28 recalibrated weights across the entire model. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.

Confirm left shoulder is documented as the infection site. Because M00.012 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.

HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for M00.012 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Confirm left shoulder is documented as the infection site
•Differentiate from right shoulder (M00.011) and unspecified shoulder (M00.019) codes

Clinical Significance

Staphylococcal arthritis of the left shoulder is a serious bacterial joint infection (septic arthritis) requiring emergency treatment to prevent permanent joint damage. Staphylococcus is the most common causative organism in septic arthritis, and infection of the shoulder joint carries risks of cartilage destruction, osteomyelitis, and systemic sepsis. Accurate site-specific coding is essential for risk adjustment and reflects the high acuity and resource needs of this condition.

Documentation Requirements

✓Provider documentation identifying Staphylococcus as the causative organism (culture results, clinical diagnosis, or documented species)
✓Documentation of the affected joint with specific anatomical site
✓Laterality documented as left side
✓Clinical findings supporting joint infection (joint effusion, warmth, erythema, limited range of motion, fever)
✓Synovial fluid analysis results or culture and sensitivity reports when available
✓Treatment documentation (antibiotics, joint aspiration, surgical drainage/washout)
✓Assessment of whether the infection is acute or chronic, and whether it is a primary infection or secondary to another source

Commonly Confused Codes

•M00.11x — Pneumococcal arthritis of same joint site; differs by causative organism (Pneumococcus vs. Staphylococcus)
•M00.21x — Streptococcal arthritis of same joint site; differs by causative organism (Streptococcus vs. Staphylococcus)
•M00.81x — Arthritis due to other bacteria at same joint site; use when organism is identified but not Staphylococcus
•M00.9 — Pyogenic arthritis, unspecified; use only when causative organism cannot be identified