ICD-10-CM > M00-M99 > M20-M25 > M21 > M21.2 > M21.26 M21.26 Flexion deformity, knee Non-Billable/Non-Specific Codes M21.261Flexion deformity, right kneeM21.262Flexion deformity, left kneeM21.269Flexion deformity, unspecified knee