ICD-10-CM Code For Osteoarthritis Of First Carpometacarpal Joint: Group Overview

The International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) code group M18 includes osteoarthritis of the first carpometacarpal joint, covering degenerative changes, primary and secondary osteoarthritis, and laterality-specific codes for thumb base arthritis. These ICD-10-CM diagnosis codes are used to document the presence, laterality, and type of thumb carpometacarpal joint osteoarthritis, capturing clinical detail such as primary versus secondary disease and any specified severity. Accurate coding within the ICD-10-CM M18 group supports proper claim adjudication, complete clinical documentation, and appropriate reimbursement.

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ICD-10-CM M18: Osteoarthritis Of First Carpometacarpal Joint Overview

The ICD-10-CM M18 group represents osteoarthritis affecting the first carpometacarpal joint at the base of the thumb, a degenerative joint disease of the hand. These diagnoses target the musculoskeletal system and specifically the carpometacarpal joint of the thumb. Accurate coding matters for clinical records and reimbursement because it reflects the specific joint involved and disease laterality and severity, which can affect claim adjudication and care planning.

When to Use

Use a code from this group when clinical documentation confirms osteoarthritis localized to the first carpometacarpal joint of the thumb. Select the code that reflects laterality and specified type when documented to ensure accurate reporting.

ICD-10-CM Codes

13 rows

ICD-10-CM Code	Description
M18.0	Bilateral primary osteoarthritis of first carpometacarpal joints
M18.10	Unilateral primary osteoarthritis of first carpometacarpal joint, unspecified hand
M18.11	Unilateral primary osteoarthritis of first carpometacarpal joint, right hand
M18.12	Unilateral primary osteoarthritis of first carpometacarpal joint, left hand
M18.2	Bilateral post-traumatic osteoarthritis of first carpometacarpal joints
M18.30	Unilateral post-traumatic osteoarthritis of first carpometacarpal joint, unspecified hand
M18.31	Unilateral post-traumatic osteoarthritis of first carpometacarpal joint, right hand
M18.32	Unilateral post-traumatic osteoarthritis of first carpometacarpal joint, left hand
M18.4	Other bilateral secondary osteoarthritis of first carpometacarpal joints
M18.50	Other unilateral secondary osteoarthritis of first carpometacarpal joint, unspecified hand
M18.51	Other unilateral secondary osteoarthritis of first carpometacarpal joint, right hand
M18.52	Other unilateral secondary osteoarthritis of first carpometacarpal joint, left hand
M18.9	Osteoarthritis of first carpometacarpal joint, unspecified

DRG Codes

2 rows

DRG Code	Description
553	Bone Diseases and Arthropathies with MCC
554	Bone Diseases and Arthropathies without MCC

Typical Clinical Scenarios

A 68-year-old woman presents to primary care with progressive, chronic pain and stiffness at the base of her dominant thumb that worsens with pinching and gripping; physical exam shows a positive grind test and reduced range of motion without signs of acute inflammation. She has long-standing functional limitation interfering with dressing and opening jars, and imaging confirms degenerative changes confined to the first carpometacarpal joint. A degenerative, primary osteoarthritic diagnosis from this group is assigned to document chronic thumb basal joint OA and guide conservative management. Typical codes: M18.0, M18.9
A 74-year-old man with a history of right thumb carpometacarpal osteoarthritis presents to orthopedics for evaluation of increasing right thumb pain, deformity, and loss of pinch strength despite conservative care; examination and recent radiographs show marked joint space narrowing and subluxation consistent with unilateral advanced disease. He is referred for surgical consideration (e.g., trapeziectomy or arthroplasty), and a specific code reflecting unilateral, severe first carpometacarpal osteoarthritis is assigned for preoperative planning and surgical documentation. Typical codes: M18.11, M18.12
A 56-year-old patient with rheumatoid arthritis is seen in rheumatology follow-up and reports focal, progressive degenerative change at the left thumb base causing pain distinct from systemic inflammatory flares; imaging shows secondary osteoarthritic changes of the first carpometacarpal joint superimposed on chronic inflammatory disease. Because the thumb joint degeneration represents secondary osteoarthritis in the setting of another joint disorder, a code from this group is used to capture the localized osteoarthritic involvement as a comorbid condition. Typical codes: M18.31, M18.32

Related Codes

M15-POLYOSTEOARTHRITIS

ICD-10-CM Code For Polyosteoarthritis: Group Overview

M16-OSTEOARTHRITIS-OF-HIP

ICD-10-CM Code For Osteoarthritis Of Hip: Group Overview

M17-OSTEOARTHRITIS-OF-KNEE

ICD-10-CM Code For Osteoarthritis Of Knee: Group Overview

M19-OTHER-AND-UNSPECIFIED-OSTEOARTHRITIS

ICD-10-CM Code For Other And Unspecified Osteoarthritis: Group Overview

Frequently Asked Questions

References

1.CPT® Codes and Descriptions. AAPC. Retrieved Aug 11, 2026.Maintains the CPT code set's official descriptions and guidelines, licensed from the American Medical Association, used as the definitional source for CPT codes on this page.
2.HCPCS Quarterly Update. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's quarterly release of HCPCS Level II codes and short/long descriptors, the source for HCPCS code definitions and update history.
3.ICD-10-CM Full Code List. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's complete ICD-10-CM diagnosis code list, used to cross-reference diagnosis codes associated with this procedure or service.

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When to Use

ICD-10-CM Codes

13 rows

ICD-10-CM Code	Description
M18.0	Bilateral primary osteoarthritis of first carpometacarpal joints
M18.10	Unilateral primary osteoarthritis of first carpometacarpal joint, unspecified hand
M18.11	Unilateral primary osteoarthritis of first carpometacarpal joint, right hand
M18.12	Unilateral primary osteoarthritis of first carpometacarpal joint, left hand
M18.2	Bilateral post-traumatic osteoarthritis of first carpometacarpal joints
M18.30	Unilateral post-traumatic osteoarthritis of first carpometacarpal joint, unspecified hand
M18.31	Unilateral post-traumatic osteoarthritis of first carpometacarpal joint, right hand
M18.32	Unilateral post-traumatic osteoarthritis of first carpometacarpal joint, left hand
M18.4	Other bilateral secondary osteoarthritis of first carpometacarpal joints
M18.50	Other unilateral secondary osteoarthritis of first carpometacarpal joint, unspecified hand
M18.51	Other unilateral secondary osteoarthritis of first carpometacarpal joint, right hand
M18.52	Other unilateral secondary osteoarthritis of first carpometacarpal joint, left hand
M18.9	Osteoarthritis of first carpometacarpal joint, unspecified

DRG Codes

2 rows

DRG Code	Description
553	Bone Diseases and Arthropathies with MCC
554	Bone Diseases and Arthropathies without MCC

Typical Clinical Scenarios

A 68-year-old woman presents to primary care with progressive, chronic pain and stiffness at the base of her dominant thumb that worsens with pinching and gripping; physical exam shows a positive grind test and reduced range of motion without signs of acute inflammation. She has long-standing functional limitation interfering with dressing and opening jars, and imaging confirms degenerative changes confined to the first carpometacarpal joint. A degenerative, primary osteoarthritic diagnosis from this group is assigned to document chronic thumb basal joint OA and guide conservative management. Typical codes: M18.0, M18.9
A 74-year-old man with a history of right thumb carpometacarpal osteoarthritis presents to orthopedics for evaluation of increasing right thumb pain, deformity, and loss of pinch strength despite conservative care; examination and recent radiographs show marked joint space narrowing and subluxation consistent with unilateral advanced disease. He is referred for surgical consideration (e.g., trapeziectomy or arthroplasty), and a specific code reflecting unilateral, severe first carpometacarpal osteoarthritis is assigned for preoperative planning and surgical documentation. Typical codes: M18.11, M18.12
A 56-year-old patient with rheumatoid arthritis is seen in rheumatology follow-up and reports focal, progressive degenerative change at the left thumb base causing pain distinct from systemic inflammatory flares; imaging shows secondary osteoarthritic changes of the first carpometacarpal joint superimposed on chronic inflammatory disease. Because the thumb joint degeneration represents secondary osteoarthritis in the setting of another joint disorder, a code from this group is used to capture the localized osteoarthritic involvement as a comorbid condition. Typical codes: M18.31, M18.32

Related Codes

M15-POLYOSTEOARTHRITIS

ICD-10-CM Code For Polyosteoarthritis: Group Overview

M16-OSTEOARTHRITIS-OF-HIP

ICD-10-CM Code For Osteoarthritis Of Hip: Group Overview

M17-OSTEOARTHRITIS-OF-KNEE

ICD-10-CM Code For Osteoarthritis Of Knee: Group Overview

M19-OTHER-AND-UNSPECIFIED-OSTEOARTHRITIS

ICD-10-CM Code For Other And Unspecified Osteoarthritis: Group Overview

Frequently Asked Questions

References

1.CPT® Codes and Descriptions. AAPC. Retrieved Aug 11, 2026.Maintains the CPT code set's official descriptions and guidelines, licensed from the American Medical Association, used as the definitional source for CPT codes on this page.
2.HCPCS Quarterly Update. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's quarterly release of HCPCS Level II codes and short/long descriptors, the source for HCPCS code definitions and update history.
3.ICD-10-CM Full Code List. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's complete ICD-10-CM diagnosis code list, used to cross-reference diagnosis codes associated with this procedure or service.

Published by

Trek Health powers OpenPayer with a leading commercial payer intelligence platform, seamlessly converting fragmented payer data into actionable insights for provider organizations.

ICD-10-CM Code For Osteoarthritis Of First Carpometacarpal Joint: Group Overview

Sign up for ICD-10-CM Code For Osteoarthritis Of First Carpometacarpal Joint: Group Overview policy alerts

ICD-10-CM M18: Osteoarthritis Of First Carpometacarpal Joint Overview

ICD-10-CM Code For Osteoarthritis Of First Carpometacarpal Joint: Group Overview

Sign up for ICD-10-CM Code For Osteoarthritis Of First Carpometacarpal Joint: Group Overview policy alerts

ICD-10-CM M18: Osteoarthritis Of First Carpometacarpal Joint Overview

When to Use

ICD-10-CM Codes

DRG Codes

Typical Clinical Scenarios

Related Codes

Which ICD-10-CM codes identify primary osteoarthritis of the first carpometacarpal joint and how is laterality indicated?

How are post-traumatic and other secondary osteoarthritis of the thumb base coded within M18?

What code should be used if the first carpometacarpal joint osteoarthritis is documented without laterality or type?

Which related DRGs are associated with diagnoses in the M18 group for billing and reimbursement context?

Why is accurate coding within the ICD-10-CM M18 group important for claims and clinical records?

References

When to Use

ICD-10-CM Codes

DRG Codes

Typical Clinical Scenarios

Related Codes

Which ICD-10-CM codes identify primary osteoarthritis of the first carpometacarpal joint and how is laterality indicated?

How are post-traumatic and other secondary osteoarthritis of the thumb base coded within M18?

What code should be used if the first carpometacarpal joint osteoarthritis is documented without laterality or type?

Which related DRGs are associated with diagnoses in the M18 group for billing and reimbursement context?

Why is accurate coding within the ICD-10-CM M18 group important for claims and clinical records?

References