Rheumatoid arthritis without rheumatoid factor, left knee

This code signifies a chronic autoimmune inflammatory condition primarily affecting the synovial lining of the left knee joint. It is characterized by the absence of rheumatoid factor (RF) in diagnostic testing, distinguishing it from seropositive rheumatoid arthritis. This form of rheumatoid arthritis can lead to joint damage, pain, and functional impairment.

This code is appropriate for patients diagnosed with seronegative rheumatoid arthritis specifically impacting the left knee. Documentation should clearly state the diagnosis of rheumatoid arthritis, specify the left knee as the affected joint, and confirm the negative status of rheumatoid factor. It would be used when the provider has explicitly ruled out or documented the absence of RF.

• Ensure documentation explicitly states "seronegative" or "rheumatoid factor negative" for rheumatoid arthritis.
• Verify the laterality (left knee) is clearly documented; do not default if unspecified.
• Distinguish from other forms of inflammatory arthritis affecting the knee, such as osteoarthritis or psoriatic arthritis.