2027 ICD-10-CM Diagnosis Code M25.171Fistula, right ankle

ICD-10-CM Codes›M00–M99›M20-M25›M25

ICD-10-CM M25.171
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

M25.171 is a billable ICD-10-CM diagnosis code for fistula, right ankle. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 555 through 556. Coders also document this condition as fistula of joint of right ankle. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified joint disorders.

Code Identity

ICD-10-CM Code
M25.171
Billable Status
Yes — Valid for Submission
Code Describes
Fistula, right ankle
Short Description
Fistula, right ankle
Same as the full description in the CMS dataset.
Parent Code
M25.17
Fistula, ankle and foot

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM20-M25Other joint disorders
CategoryM25Other joint disorder, not elsewhere classified
This CodeM25.171Fistula, right ankle

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Fistula of joint of right ankle

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to M25.171: its own notes plus those printed at M25, block M00-M25, block M20-M25, and Chapter 13. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

From Block M00-M25 applies to 2,249 codes
  • Disorders affecting predominantly peripheral (limb) joints

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From M25 Other joint disorder, not elsewhere classified applies to 225 codes
  • abnormality of gait and mobility (R26.-)
  • acquired deformities of limb (M20-M21)
  • calcification of bursa (M71.4-)
  • calcification of shoulder (joint) (M75.3)
  • calcification of tendon (M65.2-)
  • difficulty in walking (R26.2)
  • temporomandibular joint disorder (M26.6-)
From Block M20-M25 Other joint disorders applies to 719 codes
From Chapter 13 (M00-M99) Diseases of the musculoskeletal system and connective tissue applies to 6,687 codes
  • arthropathic psoriasis (L40.5-)
  • certain conditions originating in the perinatal period (P04-P96)
  • certain infectious and parasitic diseases (A00-B99)
  • compartment syndrome (traumatic) (T79.A-)
  • complications of pregnancy, childbirth and the puerperium (O00-O9A)
  • congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
  • endocrine, nutritional and metabolic diseases (E00-E88)
  • injury, poisoning and certain other consequences of external causes (S00-T88)
  • neoplasms (C00-D49)
  • symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)

Notes

General instructions on how these codes are used.

From Chapter 13 (M00-M99) Diseases of the musculoskeletal system and connective tissue applies to 6,687 codes
  • Use an external cause code following the code for the musculoskeletal condition, if applicable, to identify the cause of the musculoskeletal condition

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Clinical ClassificationClinical

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

CCSR MUS007
Other specified joint disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Fistula

    abnormal communication most commonly seen between two internal organs, or between an internal organ and the surface of the body.

Patient EducationClinical

Ankle Injuries and Disorders

Your ankle bone and the ends of your two lower leg bones make up the ankle joint. Your ligaments, which connect bones to one another, stabilize and support it. Your muscles and tendons move it.

Read the full article at MedlinePlus

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

Convert M25.171 to ICD-9-CMHistory

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

ICD-9-CM
719.87 Joint dis NEC-ankle
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 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About M25.171Overview

What is the ICD-10 code for fistula, right ankle?

The ICD-10-CM code for fistula, right ankle is M25.171 (sometimes written as M25171). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is M25.171 (Fistula, ankle and foot) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report fistula, right ankle on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does M25.171 group to?

When fistula, right ankle is the principal diagnosis on an inpatient stay, it groups to MS-DRG 555, 556, with relative weights from 0.8210 to 1.2908 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of M25.171?

Under the General Equivalence Mappings, fistula, right ankle converts to ICD-9-CM 719.87 (joint dis NEC-ankle). The mapping is approximate, so confirm the match fits the documentation.