ICD-10-CM > S00-T88 > T20-T25 > T24 > T24.4 > T24.42 > T24.421 T24.421 Corrosion of unspecified degree of right knee Non-Billable/Non-Specific Codes T24.421A..., initial encounterT24.421D..., subsequent encounterT24.421S..., sequela