ICD-10 code for knee joint inflammation

The ICD-10-CM code for knee joint inflammation is M13.169 (Monoarthritis, not elsewhere classified, unspecified knee). The official index lists 1 more specific code, so check the documentation for details such as type, cause, site or severity before settling on M13.169.

Within M13.16, choose M13.169 (unspecified knee) only when documentation doesn't support a more specific option: right knee (M13.161) and left knee (M13.162).

It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.

In MS-DRG v44.0, it is part of the grouping logic for DRG 553 (Bone Diseases and Arthropathies with MCC, relative weight 1.2494) and DRG 554 (Bone Diseases and Arthropathies without MCC, relative weight 0.8331), in MDC 08 (Diseases and Disorders of the Musculoskeletal System and Connective Tissue), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.