S56.019 Strain of flexor muscle, fascia and tendon of unspecified thumb at forearm level

ICD-10-CM S56.019: Strain of flexor muscle, fascia and tendon of unspecified thumb at forearm level

ICD-10-CM code S56.019 designates an active diagnosis for a strain affecting the flexor muscle, fascia, and tendon of an unspecified thumb at the forearm level. This diagnostic concept is classified under the broader thumb flexor strain category and is identified as an injury or poisoning event. 1

Plain-language overview

This diagnosis code identifies an injury involving a strained flexor muscle, fascia, and tendon of the thumb at the forearm level, specifically documented when the affected thumb is unspecified. 1

What this code represents

The terminology record assigns S56.019 a preferred name of strain of flexor muscle, fascia and tendon of unspecified thumb at forearm level, classifies its status as active, and assigns it the semantic type of injury or poisoning. 1

Within the coding hierarchy, S56.019 is a child concept to the parent code S56.01, which broadly covers strains of the flexor muscle, fascia, and tendon of the thumb at the forearm level. 1

Coding details

Code S56.019 has no narrower child concepts in the terminology, and available code tree listings show it expands into encounter-specific variants including S56.019A, S56.019D, and S56.019S. 1 4

While S56.019 represents the unspecified thumb diagnosis, related codes in the same category provide laterality, such as S56.011 for the right thumb and S56.012 for the left thumb at the forearm level. 4

Documentation considerations

The official terminology record for S56.019 explicitly specifies the affected thumb as unspecified, distinguishing it from related codes that designate right or left thumb laterality. 1 4

What the sources add

A clinical article describes flexor pronator tendon pathology resulting from repetitive eccentric loading or acute avulsion, establishing clinical context for flexor tendon injuries, though it does not define the target code. 2

A Medicare billing article lists specific encounter codes like S56.011A for an initial encounter, illustrating how flexor thumb strain codes appear in payer utilization contexts, though this does not guarantee coverage. 3

Comparing the sources, the terminology record establishes the official active definition and parent hierarchy for S56.019, while the code tree listing provides the subsequent encounter and sequela extensions not detailed in the primary record. 1 4

Sources

1. ICD-10-CM S56.019 terminology record — National Cancer Institute Enterprise Vocabulary Services; accessed 2026-07-27.
2. Elbow Common Flexor Tendon Repair Technique — pmc.ncbi.nlm.nih.gov; accessed 2026-07-27.
3. Article - Billing and Coding: Injections - Tendon, Ligament, Ganglion Cyst, Tunnel Syndromes and Morton's Neuroma (A57201) — cms.gov; accessed 2026-07-27.
4. ICD-10-CM 2024 | S56.01 - Strain of flexor muscle, fascia and tendon of thumb at forearm level — unboundmedicine.com; accessed 2026-07-27.