ICD-10 Code M05.661 – Rheumatoid arthritis of right knee with involvement of other organs and systems (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code M05.661 – Rheumatoid arthritis of right knee with involvement of other organs and systems
What it is
This code identifies rheumatoid arthritis affecting the right knee, with documented involvement of other organs or body systems. Use it when the record shows both the joint site and systemic manifestations.
Clinical signs
Typical findings include inflammatory joint pain, swelling, stiffness, and reduced motion in the right knee. Clinical features vary; refer to documentation for confirmed extra-articular involvement.
When to use this code
Use M05.661 when the provider documents rheumatoid arthritis in the right knee and also notes involvement of other organs or systems. The chart should support both the specific joint and the systemic nature of the disease. If the record does not confirm systemic involvement, check documentation before coding.
Do not use for
Do not use this code for rheumatoid arthritis limited to the knee without other organ or system involvement. Do not use it when the affected side is not the right knee or when the diagnosis is uncertain.
Coding tip
Verify laterality and extra-articular involvement in the provider note before assigning this code.