2027 ICD-10-CM Diagnosis Code M65.90Unspecified synovitis and tenosynovitis, unspecified site

ICD-10-CM Codes›M00–M99›M65-M67›M65

ICD-10-CM M65.90
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

M65.90 is a billable ICD-10-CM diagnosis code for unspecified synovitis and tenosynovitis, unspecified site. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 557 through 558. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Tendon and synovial disorders.

Code Identity

ICD-10-CM Code
M65.90
Billable Status
Yes — Valid for Submission
Code Describes
Unspecified synovitis and tenosynovitis, unspecified site
Short Description
Unspecified synovitis and tenosynovitis, unspecified site
Same as the full description in the CMS dataset.
Parent Code
M65.9
Synovitis and tenosynovitis, unspecified

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM65-M67Disorders of synovium and tendon
CategoryM65Synovitis and tenosynovitis
This CodeM65.90Unspecified synovitis and tenosynovitis, unspecified site

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Capsulitis of left ankle
  • Chronic synovitis
  • Chronic synovitis due to hemarthrosis
  • Enthesitis
  • SAPHO syndrome
  • Synovitis
  • Synovitis and tenosynovitis
  • Synovitis AND/OR tenosynovitis associated with another disease
  • Synovitis of ankle joint
  • Synovitis of left ankle joint
  • Tendon sheath crepitus
  • Tenoperiostitis
  • Tenosynovitis

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to M65.90: its own notes plus those printed at M65 and Chapter 13. A note printed at a category, block or chapter applies to every code under it.

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

From M65 Synovitis and tenosynovitis applies to 133 codes
  • chronic crepitant synovitis of hand and wrist (M70.0-)
  • current injury - see injury of ligament or tendon by body region
  • soft tissue disorders related to use, overuse and pressure (M70.-)

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 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.

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

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

CCSR MUS009
Tendon and synovial disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Synovitis

    inflammation of the synovial membrane.

  • Tenosynovitis

    inflammation of the synovial lining of a tendon sheath. causes include trauma, tendon stress, bacterial disease (gonorrhea, tuberculosis), rheumatic disease, and gout. common sites are the hand, wrist, shoulder capsule, hip capsule, hamstring muscles, and achilles tendon. the tendon sheaths become inflamed and painful, and accumulate fluid. joint mobility is usually reduced.

Patient EducationClinical

Joint Disorders

Your joints are places where two or more bones come together. Your shoulders, elbows, hips, knees, and knuckles are all joints. Your spine has joints, too.

The full article covers:

  • What are joints?
  • What are joint disorders?
  • What diseases can affect the joints?
  • What types of joint disorders happen from sudden injuries?
  • What types of joint disorders happen from overuse?
  • How can I keep my joints healthy?

Read the full article at MedlinePlus

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

Code History & ChangesHistory

Replacement M65.90 replaces the following previously assigned code(s):

  • M65.9 - Synovitis and tenosynovitis, unspecified
FY 2025AddedAdded to the ICD-10-CM code setEffective October 1, 2024.
FY 2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About M65.90Overview

What is the ICD-10 code for unspecified synovitis and tenosynovitis, unspecified site?

The ICD-10-CM code for unspecified synovitis and tenosynovitis, unspecified site is M65.90 (sometimes written as M6590). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is M65.90 (Synovitis and tenosynovitis, unspecified) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report unspecified synovitis and tenosynovitis, unspecified site on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does M65.90 group to?

When unspecified synovitis and tenosynovitis, unspecified site is the principal diagnosis on an inpatient stay, it groups to MS-DRG 557, 558, with relative weights from 0.8873 to 1.4883 depending on complications. Higher weights mean higher Medicare reimbursement.

Can M65.90 be reported with a code from M70.0?

Not as a rule. The Excludes1 note at M65, which applies to M65.90, lists "chronic crepitant synovitis of hand and wrist (M70.0-)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).