ICD-10 Code M02.36 – Reiter’s disease, knee (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code M02.36 – Reiter’s disease, knee
What it is
M02.36 identifies Reiter’s disease, also called reactive arthritis, affecting the knee. Use it when the record shows inflammatory arthritis linked to a preceding infection and the knee is the documented site.
Clinical signs
Typical findings include a painful, swollen, warm knee with reduced range of motion. Clinical features vary; refer to documentation for evidence of reactive arthritis and the involved joint.
When to use this code
Use M02.36 when the provider documents Reiter’s disease or reactive arthritis in the knee, even if other joints are also involved. Code it when the knee is specifically named as affected in the assessment or impression. Check documentation if the record only says arthritis after infection without site detail.
Do not use for
Do not use this code for nonspecific knee pain, osteoarthritis, or septic arthritis. If the chart does not support reactive arthritis or the knee is not documented, choose a more accurate diagnosis code.
Coding tip
Confirm both the reactive arthritis diagnosis and the knee location in the provider note before assigning M02.36.