ICD-10-CM > M00-M99 > M05-M14 > M05 > M05.6 > M05.66 M05.66 Rheumatoid arthritis of knee with involvement of other organs and systems Non-Billable/Non-Specific Codes M05.661Rheumatoid arthritis of right knee with involvement of other organs and systemsM05.662Rheumatoid arthritis of left knee with involvement of other organs and systemsM05.669Rheumatoid arthritis of unspecified knee with involvement of other organs and systems