2026 ICD-10-CM Diagnosis Code M65.261Calcific tendinitis, right lower leg

ICD-10-CM Codes›M00–M99›M65-M67›M65

ICD-10-CM M65.261
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

M65.261 is a billable ICD-10-CM diagnosis code for calcific tendinitis, right lower leg. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) 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
M65.261
Billable Status
Yes — Valid for Submission
Code Describes
Calcific tendinitis, right lower leg
Short Description
Calcific tendinitis, right lower leg
Same as the full description in the CMS dataset.
Parent Code
M65.26
Calcific tendinitis, lower leg

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM65-M67Disorders of synovium and tendon
CategoryM65Synovitis and tenosynovitis
This CodeM65.261Calcific tendinitis, right lower leg

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Bilateral calcific tendinitis of knees
  • Bilateral tendinitis of knees
  • Calcific tendinitis of bilateral lower legs
  • Calcific tendinitis of knee region
  • Calcific tendinitis of left knee
  • Calcific tendinitis of left lower leg
  • Calcific tendinitis of right knee
  • Calcific tendinitis of right lower leg
  • Tendinitis of left knee
  • Tendinitis of right knee

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

Patient EducationClinical

Tendinitis

Tendons are flexible bands of tissue that connect muscles to bones. They help your muscles move your bones. Tendinitis is the severe swelling of a tendon.

Read the full article at MedlinePlus

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

Convert M65.261 to ICD-9-CMHistory

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

ICD-9-CM
727.82 Calcium deposit tendon
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 M65.261Overview

Is M65.261 (Calcific tendinitis, lower leg) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report calcific tendinitis, right lower leg on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does M65.261 group to?

When calcific tendinitis, right lower leg is the principal diagnosis on an inpatient stay, it groups to MS-DRG 557, 558, with relative weights from 0.8932 to 1.4869 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of M65.261?

Under the General Equivalence Mappings, calcific tendinitis, right lower leg converts to ICD-9-CM 727.82 (calcium deposit tendon). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.