ICD-10 Code M05.861 – Other rheumatoid arthritis with rheumatoid factor of right knee (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code M05.861 – Other rheumatoid arthritis with rheumatoid factor of right knee
What it is
This code identifies rheumatoid arthritis with rheumatoid factor affecting the right knee, when the specific rheumatoid arthritis type is classified as other. Use it for documented RA with RF involvement limited to that joint.
Clinical signs
Typical findings include chronic inflammatory joint pain, swelling, stiffness, and reduced range of motion in the right knee. Clinical features vary; refer to documentation for rheumatoid factor positivity and joint involvement.
When to use this code
Use this code when the provider documents rheumatoid arthritis with rheumatoid factor and specifies the right knee as the affected joint. It fits cases where the diagnosis is RA, but not a more specific rheumatoid arthritis subtype.
Check documentation if the record mentions multiple joints, an unspecified knee, or a different rheumatoid arthritis category. You should code only when the right knee is clearly identified.
Do not use for
Do not use this code for rheumatoid arthritis without rheumatoid factor, or when the affected side is not the right knee. Check documentation if the diagnosis is unspecified or refers to another joint.
Coding tip
Confirm both the rheumatoid factor association and the right-knee location before assigning M05.861.