Osteoarthritis of first carpometacarpal joint (M18)

ICD-10 code M18 identifies osteoarthritis affecting the first carpometacarpal joint at the base of the thumb. These codes specify the disease’s laterality, cause (primary, post-traumatic, or secondary), and whether one or both hands are involved.

This section includes detailed codes such as M18.0 for bilateral primary osteoarthritis and M18.1 for unilateral primary cases. Common alternate terms like degenerative joint disease of thumb or osteoarthrosis of the carpometacarpal joint of the thumb correspond directly to these codes, aiding coders in accurate identification. Post-traumatic forms use codes like M18.2 (bilateral) and M18.3 (unilateral). Additionally, there are codes for other secondary osteoarthritis types (M18.4 and M18.5). The unspecified osteoarthritis of this joint is covered by M18.9. Recognizing these distinctions helps healthcare professionals document thumb joint degeneration accurately for treatment and billing.