ICD-10 code S63.491A: Traumatic rupture of left index finger ligament

Key takeaways

ICD-10 code S63.491A covers traumatic rupture of other ligament of the left index finger, initial encounter.

Right index finger injuries take S63.490A instead. In this code family an even final digit means right and an odd digit means left.

S63.491A is a billable, specific ICD-10-CM code valid for HIPAA-covered transactions. The 2026 edition took effect October 1, 2025.

The 7th character A means active treatment. Use D for a subsequent encounter and S for sequela, since the wrong character is the most common error.

Practice management software like Pabau pairs diagnosis codes with the right CPT codes and records encounter type, so claims leave complete.

S63.491A is the ICD-10-CM code for a traumatic rupture of another ligament of the left index finger, initial encounter. It is billable only with that 7th character attached.

This reference covers the official descriptor, the 7th character options, and the code hierarchy. It also covers the sibling codes coders confuse it with, the CPT pairings, and the documentation a clean claim needs.

S63.491A at a glance

S63.491A is a billable, specific ICD-10-CM diagnosis code. It covers traumatic rupture of other ligament of the left index finger at the metacarpophalangeal and interphalangeal joint, initial encounter. The table below captures the core facts coders need before submitting a claim.

What does S63.491A mean?

Every component of the S63.491A descriptor carries a specific coding meaning. Reading it as a sequence of qualifiers helps coders confirm they have the right code before submitting.

• Traumatic rupture: A complete or partial tear caused by external force, not by a degenerative or chronic process. That distinction separates it from a degenerative ligament condition coded elsewhere.
• Other ligament: Refers to ligaments of the finger that are not the collateral ligaments, which have their own codes in S63.4. “Other” in ICD-10-CM means a ligament not named in a more specific code.
• Left index finger: Laterality and digit are both coded, the index finger being the second digit of the hand. Both must be documented by the treating clinician.
• Metacarpophalangeal joint (MCP): The knuckle joint connecting the metacarpal bone of the hand to the proximal phalanx of the finger.
• Interphalangeal joint (IP): Includes the proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints of the index finger.
• Initial encounter (7th character A): The patient is receiving active treatment for this injury. This applies to the first visit and all follow-up visits during the active treatment phase.

The distinction between “other ligament” and the named ligaments matters. ICD-10-CM gives the collateral ligament its own subcategory at S63.41, the palmar ligament S63.42, and the volar plate S63.43. If the note identifies the radial or ulnar collateral ligament, S63.411A is the left index finger code instead.

If the note names no ligament at all, use S63.401A for an unspecified ligament of the left index finger. On the other hand that same code is S63.400A. Reserve S63.491A for a documented ligament that is none of the three named types.

Anatomy: metacarpophalangeal and interphalangeal joints of the index finger

Coders do not need clinical anatomy training to apply S63.491A correctly. Knowing which joints the code references does help, because it heads off documentation disputes with physicians and payers.

The index finger has three joints. The MCP joint sits at the base where the finger meets the hand. Moving distally, the PIP joint is the first knuckle along the finger shaft, and the DIP joint sits closest to the fingertip.

S63.491A covers traumatic ligament ruptures at any of these joint levels in the left index finger. The ligament involved has to be one with no named subcategory of its own.

Laterality is non-negotiable for this code. S63.491A is the left index finger, and nothing else. Billing it for a right index finger injury is a coding error, because the right-side code at these same joints is S63.490A. Practices using clinical documentation workflows that capture laterality at intake catch this before it reaches the coder.

7th character breakdown: S63.491A, S63.491D, and S63.491S

The 7th character is required for all injury codes in the S63 category. Without it, the code is not billable. The three options for S63.491 determine which phase of care is being billed.

S63.491A: Initial encounter (7th character A)

The ICD-10-CM Official Guidelines define initial encounter as the period when the patient is receiving active treatment, not just the first calendar visit. A patient seen on visit three for a wound check while still in a splint is still in the initial encounter phase. Use S63.491A as long as treatment is ongoing and directed at the acute injury.

This is the code most frequently billed for traumatic finger ligament injuries seen in urgent care, emergency departments, orthopedic practices, and hand surgery practices.

S63.491D: Subsequent encounter (7th character D)

Switch to S63.491D once active treatment has concluded and the patient is seen for monitoring, suture removal, or routine healing checks. Visit number does not drive the switch from A to D. Clinical status does. Ask whether the patient is still receiving active intervention or the injury is now healing on its own.

Rehabilitation visits after the acute phase ends take D, not A, as the 7th character. Billing A through an entire course of rehabilitation is a reliable way to attract a payer audit.

S63.491S: Sequela (7th character S)

Sequela codes apply when the patient presents with a direct late effect of the original injury. Chronic PIP joint instability is one example. Post-traumatic arthritis in the left index finger is another, provided it traces back to the prior rupture.

When using S, the sequela condition itself is typically sequenced first. S63.491S is then sequenced as an additional code to explain the cause.

Where S63.491A fits in the ICD-10-CM hierarchy

The hierarchy runs from chapter to block to category to subcategory to full code. Following it confirms specificity, and it shows when a less-specific parent code is acceptable. Category S63 also holds the dislocation and sprain subcategories, so a code like S63.638A sits alongside this one.

S63.491 without a 7th character is not a billable code. Payers reject claims that submit the base code without the encounter qualifier. The CDC ICD-10-CM code set lists the required 7th characters for every subcategory in S63.

Related and sibling codes for left index finger ligament rupture

S63.491A sits within a set of sibling codes that differ only in laterality, digit, or ligament type. Selecting the most specific applicable code is required under the ICD-10-CM Official Guidelines. A dislocation at the same joints is coded from S63.2 instead, such as S63.295D.

The split between collateral ligament codes (S63.41x) and “other ligament” codes (S63.49x) causes most of the misassignment in this family. If the note names the radial or ulnar collateral ligament of the left index finger, S63.411A applies.

If it says only “ligament rupture” with nothing named, the unspecified-ligament code S63.401A is the accurate pick. Reserve S63.491A for a ligament that is documented and is not the collateral, palmar, or volar plate.

Associated CPT codes for finger ligament repair

ICD-10 code S63.491A is a diagnosis code only. It must be paired with a CPT procedure code that describes what was done during the encounter. Which one applies depends on whether treatment is surgical or non-surgical. Neighboring hand procedures follow the same pairing logic, including arthrotomy of a finger joint under 26080.

CPT codes for ligament repair are maintained by the American Medical Association (AMA). Applicability depends on the operative or clinical documentation. Coders should not assign a surgical CPT code unless the procedure is confirmed in the physician’s note.

The device and the service are billed separately. A custom-fabricated hand and finger orthosis takes a HCPCS code such as L3913, not the CPT code for applying a stock splint. Either way, the diagnosis supports medical necessity and the procedure code describes the service rendered.

Documentation a clean claim needs

A clean S63.491A claim depends on the physician’s note containing every element the code requires. Missing any one of them triggers payer queries or automatic downcoding. Practices using digital intake and documentation forms can structure injury fields to capture each required element at the point of care.

• Laterality: The note must state “left”, or otherwise place the injury on the left hand. “Index finger ligament rupture” with no side named forces the coder down to S63.499A, the unspecified-finger code.
• Digit: “Index finger” or “second digit” must appear. “Finger ligament rupture” without digit identification is insufficient for S63.491A.
• Mechanism of injury: The note must indicate an external traumatic cause, such as a fall, an impact, forced hyperextension, or a sports injury. This separates the rupture from a degenerative or chronic process coded elsewhere.
• Ligament involved: If the physician names a collateral ligament, a code under S63.41 applies instead. If no ligament is named at all, the correct code is S63.401A. S63.491A needs a documented ligament that is not the collateral, palmar, or volar plate.
• Encounter type: The note should support the 7th character selected. For A, document active treatment such as splinting, surgery, or wound care. For D, document routine healing follow-up. For S, document the late effect and reference the original injury.
• Joint(s) affected: “At the metacarpophalangeal and/or interphalangeal joint” should appear. This is often captured implicitly through anatomical location documentation.

The CMS ICD-10-CM Official Guidelines for Coding and Reporting govern documentation requirements for injury codes. Practices billing orthopedic, hand surgery, or sports medicine services should review these guidelines every year. CMS updates them each October with the new fiscal year code set.

Four coding errors that trigger denials

Four errors account for most denials and audits on S63.491A claims. Each one is preventable at the documentation stage, before the claim is ever built.

Confusing sprain with ligament rupture

Category S63 covers both sprains and ligament ruptures at wrist and hand level. A sprain involves stretching or partial microtearing of a ligament without complete structural failure. A traumatic rupture is a complete or near-complete tear.

ICD-10-CM codes the two differently, and S63.491A is specifically for rupture. If the physician documents a sprain, the code belongs in the S63.6 sprain subcategory instead. For a left index finger sprain that code is S63.611A.

Sprain codes take the same 7th characters, so a left ring finger sprain that leaves a lasting problem is coded S63.615S. Billing S63.491A for a documented sprain is upcoding.

Incorrect 7th character selection

Continuing to bill S63.491A after active treatment has concluded is the most common error in this code family. Physical therapy for rehabilitation after a healed injury is billed with S63.491D. Payers track encounter-type patterns across claims, so a practice billing A for 12 consecutive months on one injury will draw scrutiny.

A physical therapy practice needs clear handoff documentation from the treating physician noting when active treatment ended.

Missing the external cause code

ICD-10-CM guidelines recommend an additional external cause code from the V00-Y99 chapter to describe how the injury occurred, and some payers require it. A finger ligament rupture in a basketball game, for example, takes an external cause code for contact sports activity.

Omitting it does not always trigger denial, but it can leave medical necessity thinly documented on audit. Compliance management tools that flag incomplete injury claims before they leave the practice reduce that exposure.

Using the unspecified code when laterality is documented

Billing S63.499A when the physician documented “left index finger” is a specificity error. CMS guidelines require coders to select the most specific code the documentation supports. If both side and digit are in the record, S63.491A must be used. Sports medicine software that prompts coders to verify laterality catches this before the claim reaches the payer.

How Pabau supports accurate S63.491A coding

The laterality problem usually starts long before the coder opens the chart. Side and digit sit in free text, or never make it into the note at all. The coder is then left to query the physician or drop down to S63.499A, and every query adds days to the claim.

Practice management software like Pabau lets you build the injury note as structured fields instead. Side, digit, joint, mechanism, and encounter type each get their own required entry, so the record carries what the code needs. Pabau’s claims management software then pairs that diagnosis with the CPT codes billed at the visit.

Encounter dates live in the same record, so you can see when active treatment ended and the 7th character needs to change. You get fewer physician queries, fewer unspecified codes in your denial reports, and cleaner first-pass claims.

Streamline injury billing from documentation to claim

Pabau helps orthopedic and hand surgery practices pair diagnosis codes with the right CPT codes. Track encounter types for accurate 7th character selection and submit cleaner claims.

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Conclusion

S63.491A is the left index finger code, and its right-side counterpart is S63.490A. Match the 7th character to the phase of care. Confirm side and digit in the physician’s note. Keep a true ligament rupture separate from a sprain, which belongs in S63.6.

Get those three right and denials in this code family mostly stop, without a single extra query to the physician. The trade-off sits upstream. Side, digit, ligament, and phase of care all have to be in the note before the coder opens it. To see how Pabau handles injury billing end to end, book a demo.

Continue your research

Coding the same injury on the right hand? S63.400A covers an unspecified ligament rupture of the right index finger.

Working from a sprain diagnosis instead? S63.615S shows how the finger sprain subcategory handles a sequela.

Does the note describe a dislocated joint? S63.295D covers dislocation at the distal interphalangeal joint on follow-up.

Billing a custom finger splint? L3913 sets out how a custom-fabricated hand and finger orthosis is billed.

Documenting the exam behind the code? Hand nerve tests walks through median, ulnar, and radial testing of the hand.

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