ICD-10-CM > M00-M99 > M20-M25 > M22 > M22.4 M22.4 Chondromalacia patellae Non-Billable/Non-Specific Codes M22.40Chondromalacia patellae, unspecified kneeM22.41Chondromalacia patellae, right kneeM22.42Chondromalacia patellae, left knee