Rheu arthritis w rheu factor of left knee w/o org/sys involv

This code signifies seropositive rheumatoid arthritis affecting the left knee, where the presence of rheumatoid factor (RF) has been confirmed. It indicates that the disease is localized to the joint and has not yet caused systemic complications or involvement of other organ systems.

Apply this code when documentation explicitly states a diagnosis of rheumatoid arthritis with a positive rheumatoid factor, specifically impacting the left knee. Supporting documentation should include laboratory results confirming RF positivity and clinical notes detailing left knee involvement without evidence of extra-articular manifestations.

• Ensure documentation specifies "left knee" and "rheumatoid factor positive" to accurately assign this code.
• Do not use if there is any documented organ or systemic involvement; a more specific code from the M05.7 category would be appropriate.
• Distinguish from seronegative rheumatoid arthritis (M06.0-) where rheumatoid factor is absent.