S90.559 ICD-10-CM Code: Superficial foreign body, unspecified ankle

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for S90.559 in the official ICD-10-CM tabular list, quoted as published.

Source: CMS/CDC — ICD-10-CM Tabular ListRelease: FY2026Effective: October 1, 2025

Notes without a marker are published on S90.559 itself; “inherited from” names the category or block whose note applies here.

7th Character Guide

"The appropriate 7th character is to be added to each code from category S90"

• A — initial encounter
• D — subsequent encounter
• S — sequela

How the encounter character is assigned. “Initial encounter” means the patient is receiving active treatment for the condition — it is not limited to the first visit, and a different or new provider giving active treatment still assigns it. “Subsequent encounter” covers care during the healing or recovery phase after active treatment. “Sequela” is for complications or conditions that arise as a direct result of the original condition.

ICD-10-CM Official Guidelines for Coding and Reporting, Section I.C.19.a (paraphrased by MedCoder).

Variant codes in this family

S90.559A, S90.559D, S90.559S

Character meanings are CMS's official 7th-character extensions for this family, as carried in each variant code's official description; variant codes are registry rows. The explanation of how the encounter character is assigned is MedCoder editorial, distinct from the official content above it.

Coder workflow for S90.559

MedCoder structured workflow — derived from this code’s own official record

Before you code S90.559

1. S90.559 is not reportable as written. Select the more specific code beneath it that the documentation supports. Codes are reported to the highest level of specificity the classification provides (Guidelines I.B.2).

   ReviewS90.559A, S90.559D, S90.559S

   See the relationships section · Guide: How to choose an ICD-10-CM code →

2. Unspecified does not mean incorrect. When the record gives no greater specificity, S90.559 may be the appropriate code. Check the record for detail that supports a more specific sibling. An unspecified code is for records that do not provide the detail a more specific code needs; a query, not an assumption, is the route to specificity (Guidelines I.A.9.b, I.B.18).

   ReviewS90.551, S90.552

   See the relationships section · Guide: Other vs unspecified (NEC vs NOS) →

3. A 7th character is required in this family. Confirm the documented encounter: initial (active treatment), subsequent (healing or recovery phase), or sequela. S90.559 is not valid without one. “Initial” means active treatment, not the first visit (Guidelines I.C.19.a).

   See the 7th Character Guide · Guide: 7th characters: initial, subsequent, sequela →

4. Laterality is coded in this family. Confirm the side documented — right, left, or bilateral — and select the matching code (this page’s code: unspecified). The unspecified-side code applies only when the record states no side. Laterality is assigned from the documented side; where a bilateral code exists and both sides are documented, it is used instead of two unilateral codes (Guidelines I.B.13).

   ReviewS90.551 · right, S90.552 · left

   Guide: Laterality coding →

5. Confirm the injury type, the anatomical site at the most specific level documented, laterality where the family codes it, and the encounter for the 7th character. Each injury is coded separately unless the classification provides a combination code, and a superficial injury is not coded when a more severe injury of the same site is documented. Injury chapter guidelines (Guidelines I.C.19.b, I.C.19.b.1).

   Guide: 7th characters: initial, subsequent, sequela →

Choose the right path

1. Does the documentation support one of the more specific codes beneath S90.559?
   Yes → Select that code and continue the checks below on its own page.
   No → S90.559 cannot be reported as written; query for the specificity its subcategory needs.

   ReviewS90.559A, S90.559D, S90.559S

2. Does the record document the detail a more specific sibling code needs?
   Yes → Review the specific siblings in this subcategory.
   No → Continue — S90.559 is appropriate when the documentation goes no further.

   ReviewS90.551, S90.552

3. Is the side documented?
   Yes → Select the code for the documented side (or the bilateral code when both sides are documented and one exists).
   No → Use the unspecified-side code only when the record states no side; a query is the alternative.

   ReviewS90.551 · right, S90.552 · left

4. Is the encounter phase documented — active treatment, healing or recovery, or a sequela?
   Yes → Assign the matching 7th character; the variant codes are in the 7th Character Guide.
   No → The code is invalid without its 7th character — query for the missing element.

Consider S90.559. Then confirm the code is valid for the date of service in the Verify section.

Documentation check

The provider’s diagnostic statement

Codes are assigned from the provider’s documented diagnosis, not from clinical criteria, test values or a medication list (Guidelines I.A.19).

Anatomical site

At the most specific level the record states; a site the classification separates cannot be assumed from a procedure or a measurement.

Laterality

Right, left or bilateral as documented; unspecified only when the record states no side (Guidelines I.B.13).

Encounter type

Active treatment, healing or recovery phase, or sequela — the basis of the 7th character (Guidelines I.C.19.a).

External cause, place and activity

For the external cause codes reported with the injury or poisoning, where documented (Guidelines I.C.20.a).

Any detail beyond this code’s title

What the record states that a more specific sibling code would capture — or its absence, which itself supports the unspecified code.

Official instructions as workflow

• Excludes2 — not part of S90.559(4 notes)

  Coding workflow: The conditions named in this note are not included in S90.559. When the record documents both, both may be reported; the note is a boundary, not a prohibition.

  CompareS82, T63.4

  See the official tabular notes · Guidelines I.A.12.b

Coding decision scenarios

Pattern scenarios for this code’s structure — decision rules, not clinical cases

Every row is derived from this code’s own record — its title, tabular notes, 7th-character family and same-category siblings — with fixed MedCoder wording; nothing is inferred about a patient. The official notes and guideline text are in the sections each row links to, and they control.

Don’t confuse S90.559 with…

MedCoder analysis — pairs from this code’s official notes, distinctions written by MedCoder

The codes most likely to be picked instead of S90.559 — named in its own official notes, or sharing its laterality or encounter family — with what separates them and which documentation moves the case. Each links to the full comparison.

• S90.551— Laterality relationship (Review)

  Same condition; these differ only in which side is documented.

  The same condition on the other side; the documented side decides, and a bilateral code, where one exists, replaces the pair when both sides are documented.

  What moves you there: A documented right side moves the case to S90.551.

  Full comparison: S90.559 vs S90.551 →

• S90.552— Laterality relationship (Review)

  Same condition; these differ only in which side is documented.

  The same condition on the other side; the documented side decides, and a bilateral code, where one exists, replaces the pair when both sides are documented.

  What moves you there: A documented left side moves the case to S90.552.

  Full comparison: S90.559 vs S90.552 →

• S90.559A— Encounter relationship (Review)

  Same underlying diagnosis, different encounter phase.

  The same diagnosis at a different phase of care; one encounter takes one 7th character.

  What moves you there: Documentation of a initial encounter moves the case to S90.559A.

  Full comparison: S90.559 vs S90.559A →

• S90.559D— Encounter relationship (Review)

  Same underlying diagnosis, different encounter phase.

  The same diagnosis at a different phase of care; one encounter takes one 7th character.

  What moves you there: Documentation of a subsequent encounter moves the case to S90.559D.

  Full comparison: S90.559 vs S90.559D →

• T20— Excludes2 relationship (Informational)

  Distinct conditions — both may be reported.

  A distinct condition — both may be reported when both are documented.

  What moves you there: Documentation of burns and corrosions adds T20; it is not part of this code and both may be reported when both are documented.

  Full comparison: S90.559 vs T20 →

• T32— Excludes2 relationship (Informational)

  Distinct conditions — both may be reported.

  A distinct condition — both may be reported when both are documented.

  What moves you there: Documentation of burns and corrosions adds T32; it is not part of this code and both may be reported when both are documented.

  Full comparison: S90.559 vs T32 →

Relationships are read from this code's own official notes, its laterality siblings and its encounter family; the wording of each distinction is MedCoder editorial, and the documentation named in each “what moves you there” line is the official note phrase or sibling title itself. Source: CMS ICD-10-CM tabular instructional notes; ICD-10-CM Official Guidelines, Section I.A.12.a.

Verify Before Coding

• Not billable as written — a more specific code is required: S90.559A, S90.559D, S90.559S.
• Requires a 7th character. "The appropriate 7th character is to be added to each code from category S90" Options: S90.559A, S90.559D, S90.559S

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Relationships & Classification

MedCoder structured relationships — computed from published CMS and AHRQ datasets

Other codes that name S90.559 or its code family, from the CMS ICD-10-CM tabular instructional notes. Tabular-note edges are stored at the code family level that carries each note.

Referenced by 11 Excludes2 notes: S80 — Superficial injury of knee and lower leg (via S90.-), S80-S89 — Injuries to the knee and lower leg (S80-S89) (via S90.-), S81 — Open wound of knee and lower leg (via S90.-), S82 — Fracture of lower leg, including ankle (via S90.-), S83 — Dislocation and sprain of joints and ligaments of knee (via S90.-), S84 — Injury of nerves at lower leg level (via S90.-), S85 — Injury of blood vessels at lower leg level (via S90.-), S86 — Injury of muscle, fascia and tendon at lower leg level (via S90.-), S87 — Crushing injury of lower leg (via S90.-), S88 — Traumatic amputation of lower leg (via S90.-), S89 — Other and unspecified injuries of lower leg (via S90.-).

These codes’ tabular lists name this diagnosis as distinct — both may be reported when both are documented.

Related Codes

Same condition, opposite side

Same category and title, differing only in which side of the body is affected.

S90.551 — Superficial foreign body, right ankle (right)Compare S90.559 vs S90.551 →, S90.552 — Superficial foreign body, left ankle (left)Compare S90.559 vs S90.552 →

Same Index main term, other category

The ICD-10-CM Index to Diseases and Injuries files this code under the main term “Foreign body”; these codes share that main term but sit in a different category of the Tabular List.

S50.85 — Superficial foreign body of forearm (superficial, without open wound, forearm), S60.35 — Superficial foreign body of thumb (superficial, without open wound, thumb), S60.45 — Superficial foreign body of fingers (superficial, without open wound, finger, ring), S60.459 — Superficial foreign body of unspecified finger (superficial, without open wound, finger), S60.55 — Superficial foreign body of hand (superficial, without open wound, hand), S60.85 — Superficial foreign body of wrist (superficial, without open wound, wrist), S70.25 — Superficial foreign body of hip (superficial, without open wound, hip), S70.35 — Superficial foreign body of thigh (superficial, without open wound, thigh), S80.25 — Superficial foreign body of knee (superficial, without open wound, knee), S80.85 — Superficial foreign body of lower leg (superficial, without open wound, leg), T15.0 — Foreign body in cornea (cornea), T15.1 — Foreign body in conjunctival sac (conjunctival sac), T15.8 — Foreign body in other and multiple parts of external eye (entering through orifice, eye NOS, specified part NEC), T15.9 — Foreign body on external eye, part unspecified (entering through orifice, eye NOS), T17.0 — Foreign body in nasal sinus (respiratory tract, nasal sinus), T17.1 — Foreign body in nostril (respiratory tract, nose), T17.200 — Unspecified foreign body in pharynx causing asphyxiation (pharynx, causing, asphyxiation), T17.208 — Unspecified foreign body in pharynx causing other injury (pharynx), T17.210 — Gastric contents in pharynx causing asphyxiation (pharynx, causing, asphyxiation, gastric contents), T17.218 — Gastric contents in pharynx causing other injury (pharynx, causing, injury NEC, gastric contents), +176 more

Contextual Map

Every relationship of S90.559 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Run S90.559 with these 8 related codes in Claim Check

Hierarchy

• S00-T88 — Chapter 19: Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88) (S00-T88)[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• S90-S99 — Injuries to the ankle and foot[Hierarchy]— CMS ICD-10-CM tabular structure · icd10cm-fy2026

Referenced by Excludes2 notes (11)

• S80 — Superficial injury of knee and lower leg[Excludes2](via S90.-): “superficial injury of ankle and foot (S90.-)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• S80-S89 — Injuries to the knee and lower leg (S80-S89)[Excludes2](via S90.-): “injuries of ankle and foot, except fracture of ankle and malleolus (S90-S99)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• S81 — Open wound of knee and lower leg[Excludes2](via S90.-): “injuries of ankle and foot, except fracture of ankle and malleolus (S90-S99)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• S82 — Fracture of lower leg, including ankle[Excludes2](via S90.-): “injuries of ankle and foot, except fracture of ankle and malleolus (S90-S99)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• S83 — Dislocation and sprain of joints and ligaments of knee[Excludes2](via S90.-): “injuries of ankle and foot, except fracture of ankle and malleolus (S90-S99)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• S84 — Injury of nerves at lower leg level[Excludes2](via S90.-): “injuries of ankle and foot, except fracture of ankle and malleolus (S90-S99)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• S85 — Injury of blood vessels at lower leg level[Excludes2](via S90.-): “injuries of ankle and foot, except fracture of ankle and malleolus (S90-S99)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• S86 — Injury of muscle, fascia and tendon at lower leg level[Excludes2](via S90.-): “injuries of ankle and foot, except fracture of ankle and malleolus (S90-S99)”— CMS ICD-10-CM tabular instructional notes · icd10cm-fy2026
• and 3 more

Nearest codes (40)

• S90 — Superficial injury of ankle, foot and toes[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• S90.541A — External constriction, right ankle, initial encounter[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• S90.541D — External constriction, right ankle, subsequent encounter[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• S90.541S — External constriction, right ankle, sequela[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• S90.542 — External constriction, left ankle[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• S90.542A — External constriction, left ankle, initial encounter[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• S90.542D — External constriction, left ankle, subsequent encounter[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• S90.542S — External constriction, left ankle, sequela[Sibling]— CMS ICD-10-CM tabular structure · icd10cm-fy2026
• and 32 more

Change history

• FY2016 — In the code set at ICD-10-CM adoption [Change history]— CMS release files (code change ledger) · icd10cm-fy2016

Common coding questions

Sources for this page

Codes, titles, notes, index terms and mappings on this page are transcribed from the datasets below. Relationships MedCoder computed and text MedCoder wrote are labelled where they appear.

Code, title, tabular notes and index terms Official source data

CMS/CDC ICD-10-CM FY2026 tabular list, index and tables, effective October 1, 2025 Release, file and checksum · Publisher’s page

Claim edits Official source data

CMS Definitions of Medicare Code Edits — v43.1 (April 2026) Release, file and checksum · Publisher’s page

Change history and date-of-service validity Official source data

CMS ICD-10-CM release addenda, ingested release by release into the change ledger Release, file and checksum · Publisher’s page

Comparisons, relationships and the contextual map MedCoder structured relationship

Computed by MedCoder from the tabular notes and tables above; every derived relationship is marked as derived where it appears

Summary and FAQ answers MedCoder explanation

Written by MedCoder to explain the sources above: drafted with AI assistance, checked by a person against the release files, and labelled as MedCoder text where it appears. Not official text.

Labels on this page: Official source data · MedCoder structured relationship · MedCoder explanation. How to read the labels · All data sources and release dates

Nearest Codes in This Family

Official ICD-10-CM classifications closest to S90.559 in its code family, with their registry titles.

• S90.551S — Superficial foreign body, right ankle, sequela
• S90.552 — Superficial foreign body, left ankle
• S90.552A — Superficial foreign body, left ankle, initial encounter
• S90.552D — Superficial foreign body, left ankle, subsequent encounter
• S90.552S — Superficial foreign body, left ankle, sequela
• S90.559A — Superficial foreign body, unspecified ankle, initial encounter
• S90.559D — Superficial foreign body, unspecified ankle, subsequent encounter
• S90.559S — Superficial foreign body, unspecified ankle, sequela
• S90.56 — Insect bite (nonvenomous) of ankle
• S90.561 — Insect bite (nonvenomous), right ankle

View all codes in the S90 family