ICD-10-CM > M00-M99 > M65-M67 > M66 > M66.8 > M66.83 M66.83 Spontaneous rupture of other tendons, forearm Non-Billable/Non-Specific Codes M66.831Spontaneous rupture of other tendons, right forearmM66.832Spontaneous rupture of other tendons, left forearmM66.839Spontaneous rupture of other tendons, unspecified forearm