ICD-10 Code M05.8A – Other rheumatoid arthritis with rheumatoid factor of other specified site (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code M05.8A – Other rheumatoid arthritis with rheumatoid factor of other specified site
What it is
This code identifies rheumatoid arthritis with a positive rheumatoid factor affecting a site not named in a more specific code. Use it when the record documents rheumatoid arthritis and the involved location is described as other specified.
Clinical signs
Typical findings include inflammatory joint pain, swelling, stiffness, and reduced motion. Clinical features vary; refer to documentation for the specific joint or site involved and evidence of rheumatoid factor positivity.
When to use this code
Use this code when the provider documents rheumatoid arthritis with rheumatoid factor and specifies an affected site that is not captured by a more precise ICD-10-CM option. It is appropriate when the note clearly supports rheumatoid involvement but does not name a standard site code. Check documentation if the site is unclear.
Do not use for
Do not use this code for rheumatoid arthritis without rheumatoid factor, or when a more specific site code is documented. Do not assign it if the record only says “arthritis” or the diagnosis is uncertain.
Coding tip
Confirm both the rheumatoid factor association and the exact anatomic site before coding; if the site is nonspecific, check documentation.