M18 ICD-10-CA category: Arthrosis of first carpometacarpal joint
M18 isn’t a code on its own. Choose one of the 7 codes beneath it, the one the documentation supports.
Official description
M18Arthrosis of first carpometacarpal joint
ICD-10-CA · Canada
Codes in M18
M18 isn’t a code on its own. Open the code that matches what the note documents.
M18.0Primary arthrosis of first carpometacarpal joints, bilateralM18.1Other primary arthrosis of first carpometacarpal jointM18.2Post-traumatic arthrosis of first carpometacarpal joints, bilateralM18.3Other post-traumatic arthrosis of first carpometacarpal jointM18.4Other secondary arthrosis of first carpometacarpal joints, bilateralM18.5Other secondary arthrosis of first carpometacarpal jointM18.9Arthrosis of first carpometacarpal joint, unspecifiedNotes for M18
As CIHI prints them, with any note M18 takes from the headings above it.
Includes
- Disorders affecting predominantly peripheral (limb) jointsFrom M00-M25 Arthropathies
Excludes
Conditions classified elsewhere.
- Osteoarthritis of:• spine (M47.-)• temporomandibular joint (TMJ) (K07.68)From M15-M19 Arthrosis
- Certain:• conditions originating in the perinatal period (P00-P96)• disorders of the temporomandibular joint (K07.6)• infectious and parasitic diseases (A00-B99)compartment syndrome (T79.6)complications of pregnancy, childbirth and the puerperium (O00-O99)congenital malformations, deformations and chromosomal abnormalities (Q00-Q99)endocrine, nutritional and metabolic diseases (E00-E90)injury, poisoning and certain other consequences of external causes (S00-T98)neoplasms (C00-D48)symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R99)From Chapter 13: Diseases of the musculoskeletal system and connective tissue (M00-M99)
Note
- In this block the term osteoarthritis is used as a synonym for arthrosis or osteoarthrosis. The term primary has been used with its customary clinical meaning of no underlying or determining condition identified.From M15-M19 Arthrosis
- The following fifth characters represent the following sites of involvement:0 Multiple sites1 Shoulder region: clavical , scapula — joint acromioclavicular, glenohumeral, sternoclavicular2 Upper arm: humerus — elbow joint,3 Forearm: radius , ulna — wrist joint,4 Hand: carpus, fingers, metacarpus — joints between these bones,5 Pelvic region and thigh: buttock , femur , pelvis — joint hip , sacroiliac6 Lower leg: fibula , tibia — knee joint7 Ankle and foot: metatarsus, tarsus, toes — other joints in foot8 Other:head neck ribs skull trunk vertebral column9 Site unspecifiedFrom Chapter 13: Diseases of the musculoskeletal system and connective tissue (M00-M99)
Where M18 sits
- 1ChapterChapter 13: Diseases of the musculoskeletal system and connective tissue (M00-M99)
- 2Block M00-M25Arthropathies
- 3Block M15-M19Arthrosis
- 4Category M18Arthrosis of first carpometacarpal joint
Source and release
- Data release
- ICD-10-CA · FY 2026–2027
- Effective date
- Apr 1, 2026
- Publisher
- CIHI
This page is built from the ICD-10-CA catalog that Vero Codes reads when it suggests codes: Canadian Institute for Health Information’s FY 2026–2027 release, imported from the publisher’s file and checked against it. The description, notes and structured data come from the same record.
Frequently asked questions
Is M18 a valid ICD-10-CA code?
No. M18 (Arthrosis of first carpometacarpal joint) is a category heading in CIHI’s ICD-10-CA FY 2026–2027 release. It holds 7 codes; record the one the documentation supports.
Where is M18 in ICD-10-CA?
M18 sits under M15-M19 Arthrosis, within M00-M25 Arthropathies, within Chapter 13: Diseases of the musculoskeletal system and connective tissue (M00-M99).
What coding notes apply to M18?
ICD-10-CA lists Note, Excludes, Includes notes for M18, including those from the headings it sits under. They are listed on this page with where each one comes from.
Which ICD-10-CA release does this page use?
It uses CIHI’s FY 2026–2027 release, in effect from Apr 1, 2026 to Mar 31, 2027. It is a reference: confirm the code against the current list and the payer’s rules before you submit it.