S80.221ABlister (nonthermal), right knee, initial encounter

S80.221A is the ICD-10-CM diagnosis code for Blister (nonthermal), right knee, initial encounter. It belongs to category S80 (superficial injury of knee and lower leg), block S80-S89 (injuries to the knee and lower leg) and chapter 19 (injury, poisoning and certain other consequences of external causes). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

The 7th character "A" means initial encounter: use it while the patient is receiving active treatment for the condition.

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 606 (Minor Skin Disorders with MCC, relative weight 1.5728), DRG 607 (Minor Skin Disorders without MCC, relative weight 0.8772), DRG 963 (Other Multiple Significant Trauma with MCC, relative weight 2.6363), DRG 964 (Other Multiple Significant Trauma with CC, relative weight 1.4972) and DRG 965 (Other Multiple Significant Trauma without CC/MCC, relative weight 1.0059), in MDC 09 (Diseases and Disorders of the Skin, Subcutaneous Tissue and Breast) and MDC 24 (Multiple Significant Trauma), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Before ICD-10, this condition was coded in ICD-9-CM as 916.2 (Blister of hip, thigh, leg, and ankle, without mention of infection).