Osteoarthritis of first carpometacarpal joint, unspecified

This code signifies degenerative joint disease affecting the base of the thumb, specifically the articulation between the trapezium and the first metacarpal bone, without further specification of laterality or severity. It involves the breakdown of cartilage and underlying bone, leading to pain, stiffness, and impaired function of the thumb.

Apply this code when documentation indicates osteoarthritis of the first carpometacarpal (CMC) joint but does not specify if it's right, left, or bilateral. This is appropriate for initial diagnoses or when laterality is unknown or not explicitly stated by the provider.

• Avoid using this code if laterality (right, left, bilateral) is documented; instead, use the more specific M18.1- or M18.2-.
• Ensure the documentation clearly states "osteoarthritis" and specifies the "first carpometacarpal joint."
• Do not confuse with other hand osteoarthritis codes (e.g., M19.- for other specified primary osteoarthritis).