ICD-10-CM > S00-T88 > S80-S89 > S83 > S83.1 > S83.12 > S83.121 S83.121 Posterior subluxation of proximal end of tibia, right knee Non-Billable/Non-Specific Codes S83.121A..., initial encounterS83.121D..., subsequent encounterS83.121S..., sequela