M00.09

Staphylococcal pyogenic arthritis affecting multiple joints simultaneously, not limited to a single anatomical site.

Verified May 8, 2026 · 5 sources ↓

Status: Billable
Chapter: 13
Related CPT: 10
Region: Multi-region

Drawn from CDCICD10DataCMSAAPC

Documentation tips

What should appear in the chart to support M00.09.

Source · Editorial brief grounded in 5 cited references ↓

Name the specific Staphylococcus species (MSSA, MRSA, or unspecified) so the required B95.6x/B95.8 secondary code can be accurately assigned.
Document all affected joints by name — 'polyarthritis' requires more than one joint to be clinically identified and confirmed infected.
Record the method of organism identification: culture source (blood, synovial fluid, wound), gram stain result, and sensitivity profile.
Note the absence of an internal joint prosthesis in any affected joint — if a prosthesis is present, the encounter routes to T84.5- instead of M00.09.
For inpatient encounters, document all comorbidities and complications explicitly so the correct MCC/CC tier for DRG 548/549/550 is supported.

Related CPT procedures

Procedure codes commonly billed with M00.09. Linking the right diagnosis to the right procedure is what establishes medical necessity.

Source · CMS LCDs · AAOS specialty guidance · claims-pattern analysis

20600 $56.11

Needle aspiration and/or injection of a small joint or bursa — such as a finger or toe joint — performed without ultrasound guidance.

20604 $87.18

Arthrocentesis, aspiration and/or injection of a small joint or bursa (e.g., fingers, toes) performed with ultrasound guidance, including permanent image recording and reporting.

20605 $57.12

Aspiration and/or injection of an intermediate joint or bursa — such as the wrist, elbow, ankle, acromioclavicular joint, or olecranon bursa — performed without ultrasound guidance.

20606 $94.19

Aspiration and/or injection of an intermediate joint or bursa — such as the wrist, elbow, ankle, acromioclavicular, temporomandibular, or olecranon bursa — performed with real-time ultrasound guidance and permanent image recording and reporting.

20610 $68.81

Aspiration and/or injection of a major joint or bursa (shoulder, hip, knee, or subacromial bursa) performed without ultrasound guidance.

20611 $104.21

Aspiration or injection of a major joint or bursa performed under real-time ultrasound guidance, with permanent image documentation.

27310 $689.06

Open arthrotomy of the knee for exploration, drainage of infection, or removal of a foreign body or loose material from the joint space.

27380 $597.88

Primary open suture repair of the infrapatellar (patellar) tendon performed within days of acute injury.

23040 $673.03

Open arthrotomy of the glenohumeral joint for exploration, drainage of fluid or infection, and/or removal of a foreign body.

29800 $508.70

Diagnostic arthroscopy of the temporomandibular joint (TMJ), with or without synovial biopsy, performed as a separate procedure.

Common coding pitfalls

The recurring mistakes coders make with M00.09 and adjacent codes.

Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓

Omitting the required B95 secondary code to identify the staphylococcal agent — the parent M00.0 tabular annotation mandates it.
Using M00.09 when only one joint is documented as infected — single-joint staphylococcal arthritis requires a site-specific M00.0x code with laterality.
Applying M00.09 to a patient with a prosthetic joint — infection of an internal joint prosthesis is excluded from M00 and maps to T84.5-.
Confusing M00.09 with M00.9 (pyogenic arthritis, unspecified organism) — M00.09 is organism-specific and requires documented or confirmed staphylococcal etiology.

Clinical context

Source · Editorial summary grounded in 5 cited references ↓

M00.09 captures staphylococcal infection involving multiple joints concurrently — the polyarticular presentation of the M00.0 family. Use it when culture, gram stain, or clinical documentation confirms Staphylococcus as the causative organism and more than one joint is involved. Single-joint staphylococcal septic arthritis maps to a site-specific M00.0x code (e.g., M00.011 for the right shoulder); M00.09 is reserved exclusively for the multi-joint pattern.

The parent code M00.0 carries a 'Use Additional Code' instruction: always append a B95 code to identify the specific staphylococcal agent — B95.61 for MSSA, B95.62 for MRSA, or B95.8 for unspecified Staphylococcus. Omitting this secondary code leaves the organism undocumented and can trigger payer audit flags. M00.09 is also explicitly excluded from use when the infection is associated with an internal joint prosthesis — those cases fall under T84.5-.

MS-DRG v43.0 routes M00.09 into DRGs 548 (Septic Arthritis with MCC), 549 (with CC), or 550 (without CC/MCC). Accurate capture of comorbidities and complications that qualify as MCC or CC directly affects DRG assignment and reimbursement tier. Orthopedic coders working in inpatient settings should verify that the clinical documentation supports the appropriate CC/MCC level before final code submission.

Sibling codes

Other billable codes under M00.0 (laterality / anatomic variants).

M00.08

Staphylococcal arthritis, vertebrae

M00.00

Staphylococcal arthritis, unspecified joint

Frequently asked questions

Source · Generated from the editorial pipeline, verified against 5 cited references ↓

01What secondary code must always accompany M00.09?

A B95 code is required: B95.61 for MSSA, B95.62 for MRSA, or B95.8 for Staphylococcus unspecified. The M00.0 parent tabular annotation explicitly instructs 'Use Additional code (B95.61–B95.8) to identify bacterial agent.'

02How many joints must be involved to use M00.09 instead of a site-specific M00.0x code?

More than one joint must be documented as infected. If only a single joint is affected, select the appropriate site-specific M00.0x code with the correct laterality character.

03Can M00.09 be used when the patient has an infected prosthetic joint?

No. The M00 category carries a Type 2 Excludes note for infection and inflammatory reaction due to internal joint prosthesis. Those cases map to T84.5- codes, not M00.09.

04Which DRGs does M00.09 map to for inpatient billing?

MS-DRG v43.0 assigns M00.09 to DRG 548 (Septic Arthritis with MCC), 549 (with CC), or 550 (without CC/MCC), depending on documented comorbidities and complications.

05Is M00.09 valid for outpatient encounters or only inpatient?

M00.09 is a billable code valid for both inpatient and outpatient settings. The DRG groupings are inpatient-specific, but the code itself can be used in any care setting where staphylococcal polyarthritis is the confirmed diagnosis.

06What is the difference between M00.09 and M00.9?

M00.09 specifies Staphylococcus as the confirmed causative organism across multiple joints. M00.9 is pyogenic arthritis with the organism unspecified — it is a fallback code and should not be used when the pathogen is identified.

07Does M00.09 require documentation of imaging findings?

Imaging is not required for code assignment, but documenting joint X-rays, MRI findings, or ultrasound-guided aspiration results strengthens medical necessity and supports the polyarticular nature of the infection for payer review.

Sources & references

Editorial content was developed using the following public sources. Last verified May 8, 2026.

01CDC ICD-10-CM Tabular List 2026 (effective Oct 1, 2025)
02
icd10data.com
https://www.icd10data.com/ICD10CM/Codes/M00-M99/M00-M02/M00-/M00.09
03
cms.gov
https://www.cms.gov/medicare-coverage-database/view/article.aspx?articleid=58865&ver=19
04
cms.gov
https://www.cms.gov/medicare-coverage-database/view/article.aspx?articleid=58747&ver=50
05
aapc.com
https://www.aapc.com/codes/icd-10-codes/M00.09

Mira AI Scribe

Mira's AI scribe captures the number and names of affected joints, the organism identified (MSSA vs. MRSA vs. unspecified staph), the diagnostic source (synovial fluid culture, blood culture, gram stain), and any documented prosthetic joint involvement — preventing the missing B95 secondary code, a single-joint miscategorization, and the prosthesis exclusion error that together are the top audit triggers for M00.09.

See how Mira captures M00.09 documentation