2026 ICD-10-CM Diagnosis Code T84.023SInstability of internal left knee prosthesis, sequela

ICD-10-CM Codes›S00–T88›T80-T88›T84

ICD-10-CM T84.023S
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

T84.023S is a billable ICD-10-CM diagnosis code for instability of internal left knee prosthesis, sequela. The 7th character S marks it as a sequela code, which reports a problem that remains after the original condition has resolved. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 922 through 923. The code is exempt from POA reporting. Coders also document this condition as dislocation of knee joint prosthesis. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Complication, sequela.

Code Identity

ICD-10-CM Code
T84.023S
Billable Status
Yes — Valid for Submission
Code Describes
Instability of internal left knee prosthesis, sequela
Short Description
Instability of internal left knee prosthesis, sequela
Same as the full description in the CMS dataset.
Parent Code
T84.023
Instability of internal left knee prosthesis

Code Classification

ChapterS00–T88Injury, poisoning and certain other consequences of external causes
SectionT80-T88Complications of surgical and medical care, not elsewhere classified
CategoryT84Complications of internal orthopedic prosthetic devices, implants and grafts
This CodeT84.023SInstability of internal left knee prosthesis, sequela

Present on Admission (POA)Billing

T84.023S is exempt from POA reporting on inpatient claims to general acute care hospitals. Review other POA exempt codes.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Dislocation of knee joint prosthesis
  • Dislocation of left knee joint prosthesis
  • Instability of joint of left knee
  • Instability of prosthesis of joint of knee
  • Instability of prosthetic left knee joint
  • Left knee subluxation
  • Subluxation of knee joint prosthesis
  • Subluxation of left knee joint prosthesis

Coding GuidelinesGuidance

The appropriate 7th character is to be added to each code from block Complications of internal orthopedic prosthetic devices, implants and grafts (T84). Use the following options for the applicable episode of care:

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

Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2026, published by CMS and the National Center for Health Statistics.

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR INJ076
Complication, sequela
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Knee Replacement

Knee replacement surgery is a surgery to replace parts of your knee joint with new, artificial parts. You may need a knee replacement if you have knee damage that causes severe pain and difficulty doing daily activities, such as walking and climbing stairs. It is usually done when other treatments for knee pain haven't helped enough.

The full article covers:

  • What is knee replacement surgery?
  • What conditions does knee replacement surgery treat?
  • What happens during knee replacement surgery?
  • What happens after knee replacement surgery?
  • What is life like after a knee replacement?
  • What are the risks of knee replacement surgery?
  • How long does a knee replacement last?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert T84.023S to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
909.3 Late eff surg/med compl
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About T84.023SOverview

Is T84.023S (Instability of internal left knee prosthesis) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report instability of internal left knee prosthesis, sequela on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What does the 7th character S in T84.023S mean?

The final character S makes this a sequela code: it reports a lingering problem that remains after the instability of internal left knee prosthesis itself has resolved, not the original event.

What MS-DRG does T84.023S group to?

When instability of internal left knee prosthesis, sequela is the principal diagnosis on an inpatient stay, it groups to MS-DRG 922, 923, with relative weights from 1.0177 to 1.7494 depending on complications. Higher weights mean higher Medicare reimbursement.

Is T84.023S exempt from POA reporting?

Yes. CMS lists this code among those exempt from present on admission reporting, so hospitals do not assign a POA indicator for instability of internal left knee prosthesis, sequela on inpatient claims.

What is the ICD-9 equivalent of T84.023S?

Under the General Equivalence Mappings, instability of internal left knee prosthesis, sequela converts to ICD-9-CM 909.3 (late eff surg/med compl). The mapping is approximate, so confirm the match fits the documentation.