Is ICD-10-CM code M23 billable?

No, M23 (Internal derangement of knee) is a non-billable ICD-10-CM code. It must be coded to a more specific subcategory before it can be used for reimbursement.

What chapter does ICD-10-CM code M23 belong to?

M23 belongs to Chapter 13 of the ICD-10-CM tabular list: M00–M99 (Diseases of the Musculoskeletal System and Connective Tissue).

M23Not billable, use a more specific code below

Internal derangement of knee

In Other joint disorders (M20-M25), chapter 13: Diseases of the Musculoskeletal System and Connective Tissue

111 billable codes under M23: none are a CC or MCC; none map to an HCC.

Instructional notes

Excludes1: not coded here, use a different code

ankylosis (M24.66)
deformity of knee (M21.-)
osteochondritis dissecans (M93.2)

Excludes2: not included here, code separately if applicable

current injury - see injury of knee and lower leg (S80-S89)
recurrent dislocation or subluxation of joints (M24.4)
recurrent dislocation or subluxation of patella (M22.0-M22.1)

Also applies, from Other joint disorders (M20-M25)

These notes sit on M20-M25 and apply to every code under it, including M23.

Excludes2: not included here, code separately if applicable

joints of the spine (M40-M54)

Official coding guidelines

From the ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027 (CMS and NCHS). Links open the PDF at the right page.

Covers site and laterality, acute injury versus chronic musculoskeletal conditions, 7th characters for pathologic fractures, osteoporosis with or without current fracture, and multisystem inflammatory syndrome.

Site and laterality (page 60)
Acute traumatic versus chronic or recurrent musculoskeletal conditions (page 61)
Coding of Pathologic Fractures (page 61)
Osteoporosis (page 61)
Multisystem Inflammatory Syndrome (page 62)

Read Section I.C.13 (page 60)

All codes under M23

M23 can't be used on a claim. Pick a billable code below; grey headings group them.

M23 MS-DRGs

As the principal diagnosis, the billable codes under M23 group to MS-DRG 562, 563, 564, 565, or 566 (v44.0). Which one applies depends on procedures performed, secondary diagnoses (CC/MCC), and the patient's age and discharge status.

DRG 562 Fracture, Sprain, Strain and Dislocation Except Femur, Hip, Pelvis and Thigh with MCC (105 of 111 codes)
DRG 563 Fracture, Sprain, Strain and Dislocation Except Femur, Hip, Pelvis and Thigh without MCC (105 of 111 codes)
DRG 564 Other Musculoskeletal System and Connective Tissue Diagnoses with MCC (6 of 111 codes)
DRG 565 Other Musculoskeletal System and Connective Tissue Diagnoses with CC (6 of 111 codes)
DRG 566 Other Musculoskeletal System and Connective Tissue Diagnoses without CC/MCC (6 of 111 codes)

Other codes that refer to M23

Notes on these codes point to M23.

M24.1 Excludes2: internal derangement of knee (M23.-)
S83 Excludes2: internal derangement of knee (M23.-)

About the condition

Plain-language background from MedlinePlus (National Library of Medicine), not coding guidance.

Knee Injuries and Disorders

Your knee joint is made up of bone, cartilage, ligaments and fluid. Muscles and tendons help the knee joint move. When any of these structures is hurt or diseased, you have knee problems. Knee problems can cause pain and difficulty walking.

Code history

Valid since FY2016, when ICD-10-CM took effect on October 1, 2015. No changes since.