S66.510D Strain of intrinsic muscle, fascia and tendon of right index finger at wrist and hand level, subsequent encounter

ICD-10-CM S66.510D: Strain of intrinsic muscle, fascia and tendon of right index finger at wrist and hand level, subsequent encounter

ICD-10-CM code S66.510D identifies a strain of the intrinsic muscle, fascia, and tendon of the right index finger at the wrist and hand level for a subsequent encounter. The code is listed within injury categories for the wrist, hand, and fingers. Public sources establish the code's official descriptor and its placement in injury coding contexts, but do not provide complete clinical guidelines or coverage rules. 3 1

Plain-language overview

Code S66.510D is labeled as a strain of the intrinsic muscle, fascia, and tendon of the right index finger at the wrist and hand level, and it is explicitly associated with a subsequent encounter in the source code tree. 3

What this code represents

The code S66.510D is categorized under the S60-S69 block for injuries to the wrist, hand, and fingers, appearing alongside other specific finger injury codes such as lacerations and flexor strains. 3

Coding details

The source listing places S66.510D next to the bracketed notation [subsequent encounter], while a separate right index finger strain code, S66.310A, is listed with the notation [initial encounter]. 3

The S60-S69 injury block contains distinct codes for right and left sides, such as S66.510D for the right index finger and S66.515D for the left ring finger, both designated as subsequent encounters. 3

Documentation considerations

The supplied excerpts provide the official descriptor and code tree placement for S66.510D, but they do not explicitly state the documentation elements needed for accurate code selection. 3

Coverage and utilization context

A Centers for Medicare and Medicaid Services billing and coding article for tendon, ligament, and tunnel injections lists specific ICD-10-CM strain codes, including S66.310A and S66.311A for right and left index finger extensor strains. 1 2

The CMS article is titled for billing and coding of injections and includes tendon injury codes, but the supplied excerpts do not explicitly state whether S66.510D is included in that article or make any statements regarding coverage guarantees. 1 2

What the sources add

The CMS billing article lists extensor strain codes for the index finger, while the Unbound Medicine code tree lists S66.510D as an intrinsic muscle strain, showing that different sources provide distinct operational and code-level contexts for finger strain injuries. 1 3

Questions to verify

The supplied sources do not establish whether the CMS injection billing article explicitly includes S66.510D among its listed diagnosis codes, indicating a need to verify the exact code list applied to injection services. 1 3

Sources

1. Article - Billing and Coding: Injections - Tendon, Ligament, Ganglion Cyst, Tunnel Syndromes and Morton's Neuroma (A57079) — cms.gov; accessed 2026-07-25.
2. Article - Billing and Coding: Injections - Tendon, Ligament, Ganglion Cyst, Tunnel Syndromes and Morton's Neuroma (A57079) — cms.gov; accessed 2026-07-25.
3. ICD-10-CM 2024 | S60-S69 - Injuries to the wrist, hand and fingers — unboundmedicine.com; accessed 2026-07-25.