ICD-10-CM > S00-T88 > S50-S59 > S56 > S56.0 > S56.01 S56.01 Strain of flexor muscle, fascia and tendon of thumb at forearm level Non-Billable/Non-Specific Codes S56.011Strain of flexor muscle, fascia and tendon of right thumb at forearm levelS56.011A..., initial encounterS56.011D..., subsequent encounterS56.011S..., sequelaS56.012Strain of flexor muscle, fascia and tendon of left thumb at forearm levelS56.012A..., initial encounterS56.012D..., subsequent encounterS56.012S..., sequelaS56.019Strain of flexor muscle, fascia and tendon of unspecified thumb at forearm levelS56.019A..., initial encounterS56.019D..., subsequent encounterS56.019S..., sequela