ICD-10 Code M05.669 – Rheumatoid arthritis of unspecified knee with involvement of other organs and systems (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code M05.669 – Rheumatoid arthritis of unspecified knee with involvement of other organs and systems
What it is
This code identifies rheumatoid arthritis affecting an unspecified knee and also involving other organs or body systems. Use it when the record shows rheumatoid disease with systemic involvement, but the knee laterality is not specified.
Clinical signs
Typical findings include inflammatory joint pain, swelling, stiffness, and reduced range of motion in the knee. Clinical features vary; refer to documentation for evidence of extra-articular or systemic involvement.
When to use this code
Use this code when the provider documents rheumatoid arthritis of a knee and does not specify right or left. It also requires mention of involvement beyond the joint, such as another organ or system. If the chart does not clearly support systemic involvement, check documentation.
Do not use for
Do not use this code for rheumatoid arthritis limited to the knee alone. It is also incorrect when the affected knee is documented as right or left and a more specific code is available.
Coding tip
Confirm both the unspecified knee and the extra-articular involvement before assigning M05.669.