ICD-10 Code M06.06 – Rheumatoid arthritis without rheumatoid factor, knee (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code M06.06 – Rheumatoid arthritis without rheumatoid factor, knee
What it is
This code identifies rheumatoid arthritis that affects the knee and is documented without a rheumatoid factor. Use it when the provider specifies seronegative rheumatoid arthritis in the knee.
Clinical signs
Typical findings include persistent knee pain, swelling, stiffness, and reduced range of motion. Clinical features vary; refer to documentation for joint involvement and whether rheumatoid factor is absent.
When to use this code
Use M06.06 when the record clearly states rheumatoid arthritis without rheumatoid factor involving the knee. It is appropriate for laterality-neutral documentation that names the knee but does not specify a different rheumatoid arthritis subtype.
Check documentation if the note only says inflammatory arthritis, rheumatoid arthritis, or seronegative arthritis without confirming the knee or the absence of rheumatoid factor.
Do not use for
Do not use this code for rheumatoid arthritis with positive rheumatoid factor, other joints, or nonspecific knee pain. If the diagnosis is unclear, check documentation.
Coding tip
Code only when both the joint and the seronegative rheumatoid arthritis diagnosis are explicitly documented.