Felty's syndrome, left knee

This code signifies Felty's syndrome affecting the left knee. Felty's syndrome is a rare, severe complication of rheumatoid arthritis characterized by the triad of rheumatoid arthritis, splenomegaly, and neutropenia. The specific joint involvement in this case is the left knee.

Use this code when documentation clearly indicates a diagnosis of Felty's syndrome with specific involvement of the left knee joint. This typically applies to patients with long-standing, severe rheumatoid arthritis who present with symptoms related to their left knee, alongside evidence of splenomegaly and neutropenia. Supporting documentation would include physician notes detailing the diagnosis, imaging reports confirming left knee pathology, and laboratory results showing neutropenia.

• Ensure documentation explicitly states "Felty's syndrome" and specifies "left knee" involvement; do not assume knee involvement from general rheumatoid arthritis.
• Always code the underlying rheumatoid arthritis (e.g., M05.xx) as the primary diagnosis if not already captured, followed by this code for the specific manifestation.
• Verify laterality; if the right knee or bilateral knees are affected, a different code is required.