ICD-10-CM > M00-M99 > M65-M67 > M66 > M66.2 > M66.26 M66.26 Spontaneous rupture of extensor tendons, lower leg Non-Billable/Non-Specific Codes M66.261Spontaneous rupture of extensor tendons, right lower legM66.262Spontaneous rupture of extensor tendons, left lower legM66.269Spontaneous rupture of extensor tendons, unspecified lower leg