2027 ICD-10-CM Diagnosis Code M99.9Biomechanical lesion, unspecified

ICD-10-CM Codes›M00–M99›M99›M99

ICD-10-CM M99.9
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

M99.9 is a billable ICD-10-CM diagnosis code for biomechanical lesion, unspecified. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 564 through 566. Coders also document this condition as lesion of lumbar spine. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Biomechanical lesions.

Code Identity

ICD-10-CM Code
M99.9
Billable Status
Yes — Valid for Submission
Code Describes
Biomechanical lesion, unspecified
Short Description
Biomechanical lesion, unspecified
Same as the full description in the CMS dataset.
Parent Code
M99
Biomechanical lesions, not elsewhere classified

Code Classification

ChapterM00–M99Diseases of the musculoskeletal system and connective tissue
SectionM99Biomechanical lesions, not elsewhere classified
CategoryM99Biomechanical lesions, not elsewhere classified
This CodeM99.9Biomechanical lesion, unspecified

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Lesion of lumbar spine
  • Lesion of thoracic spine
  • Stenosis of intervertebral foramina

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to M99.9: its own notes plus those printed at M99 and Chapter 13. A note printed at a category, block or chapter applies to every code under it.

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 M99 Biomechanical lesions, not elsewhere classified applies to 91 codes
  • This category should not be used if the condition can be classified elsewhere.
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.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name M99.9, its category, or a range that includes it.

Excludes1 1

These codes carry an Excludes1 note naming M99.9: they are not reported together with it, unless the two conditions are unrelated.

  • M43.5 Other recurrent vertebral dislocation
    biomechanical lesions NEC (M99.-) names M99.-, which includes this code

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 MUS012
Biomechanical lesions
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Biomechanical Lesion

    a localized defect of soft tissue or bone that results in the altered function of an associated anatomic structure.

Convert M99.9 to ICD-9-CMHistory

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

ICD-9-CM
738.9 Acq deformity NOS
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 M99.9Overview

What is the ICD-10 code for biomechanical lesion, unspecified?

The ICD-10-CM code for biomechanical lesion, unspecified is M99.9 (sometimes written as M999). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is M99.9 (Biomechanical lesions, not elsewhere classified) a billable code?

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

What MS-DRG does M99.9 group to?

When biomechanical lesion, unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 564, 566, 565, with relative weights from 0.7374 to 1.4909 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of M99.9?

Under the General Equivalence Mappings, biomechanical lesion, unspecified converts to ICD-9-CM 738.9 (acq deformity NOS). The mapping is approximate, so confirm the match fits the documentation.