ICD-10-CM > S00-T88 > S80-S89 > S80 > S80.2 > S80.22 > S80.229 S80.229 Blister (nonthermal), unspecified knee Non-Billable/Non-Specific Codes S80.229A..., initial encounterS80.229D..., subsequent encounterS80.229S..., sequela