M00.261
Other streptococcal arthritis, right knee
M00.261 (also written M00261) is a billable ICD-10-CM diagnosis code for other streptococcal arthritis, right knee. It is part of the FY2027 code set, effective October 1, 2026. It is one of the 97 codes in category M00 (Pyogenic arthritis). Its coding notes include a Use additional code instruction and 11 Excludes2 entries.
Use additional code
Add the listed code as a secondary code, if known.
Excludes2
Not included here. Both codes may be reported if the patient has both conditions.
- infection and inflammatory reaction due to internal joint prosthesis (T84.5-)
Also from chapter/block level (10 notes)
- arthropathic psoriasis (L40.5-)
- certain conditions originating in the perinatal period (P04-P96)
- certain infectious and parasitic diseases (A00-B99)
- compartment syndrome (traumatic) (T79.A-)
- complications of pregnancy, childbirth and the puerperium (O00-O9A)
- congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
- endocrine, nutritional and metabolic diseases (E00-E88)
- injury, poisoning and certain other consequences of external causes (S00-T88)
- neoplasms (C00-D49)
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)
Care settings
How CMS programs treat this code. These are CMS claim edits and list entries, not coverage or eligibility rules.
Home Health Primary
Accepted as the primary (principal) diagnosis on a home health claim. The Home Health Grouper assigns it to the Musculoskeletal Rehabilitation clinical group.
Source: CMS Home Health Grouper Software v07.2.26, effective October 1, 2026Hospital CC
Counts as a complication or comorbidity (CC) when reported as a secondary diagnosis on an inpatient claim. It does not count when the principal diagnosis is one of the 447 codes in its exclusion list. Some MS-DRGs also ignore a CC or MCC that defines the DRG.
Source: CMS MS-DRG Definitions Manual v44, effective October 1, 2026, Appendix CNotes
Also from chapter/block level (4 notes)
- This block comprises arthropathies due to microbiological agents. Distinction is made between the following types of etiological relationship:
- a) direct infection of joint, where organisms invade synovial tissue and microbial antigen is present in the joint;
- b) indirect infection, which may be of two types: a reactive arthropathy, where microbial infection of the body is established but neither organisms nor antigens can be identified in the joint, and a postinfective arthropathy, where microbial antigen is present but recovery of an organism is inconstant and evidence of local multiplication is lacking.
- Use an external cause code following the code for the musculoskeletal condition, if applicable, to identify the cause of the musculoskeletal condition