ICD-10 Code M05.86 – Other rheumatoid arthritis with rheumatoid factor of knee (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code M05.86 – Other rheumatoid arthritis with rheumatoid factor of knee
What it is
This code identifies rheumatoid arthritis with rheumatoid factor affecting the knee, but not a more specific rheumatoid arthritis subtype. Use it when the record documents RA with RF and knee involvement.
Clinical signs
Typical findings include inflammatory joint pain, swelling, stiffness, and reduced knee range of motion. Clinical features vary; refer to documentation, especially for evidence of rheumatoid factor and the involved joint.
When to use this code
Use this code when the provider documents rheumatoid arthritis with rheumatoid factor and specifies the knee as the affected site. It also fits cases where the knee is one of multiple involved joints and this diagnosis is clearly stated. Check documentation if the note does not confirm rheumatoid factor or joint site.
Do not use for
Do not use it for rheumatoid arthritis without rheumatoid factor, or when the diagnosis is only suspected. Do not code it for nonspecific knee pain, osteoarthritis, or if documentation does not support RA involvement.
Coding tip
Verify both the rheumatoid factor association and the knee location in the provider note before assigning M05.86.