ICD-10-CM > M00-M99 > M65-M67 > M66 > M66.3 > M66.37 M66.37 Spontaneous rupture of flexor tendons, ankle and foot Non-Billable/Non-Specific Codes M66.371Spontaneous rupture of flexor tendons, right ankle and footM66.372Spontaneous rupture of flexor tendons, left ankle and footM66.379Spontaneous rupture of flexor tendons, unspecified ankle and foot