ICD-10 Code M00.161 – Pneumococcal arthritis, right knee (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code M00.161 – Pneumococcal arthritis, right knee
What it is
M00.161 identifies pneumococcal infection of the right knee joint causing septic arthritis. Use it when documentation confirms Streptococcus pneumoniae as the organism and the right knee is the affected site.
Clinical signs
Typical findings include an acutely painful, swollen, warm knee with limited range of motion. Fever may occur, and joint aspiration or culture may support the organism identification. Clinical features vary; refer to documentation.
When to use this code
Use this code when the provider documents pneumococcal septic arthritis specifically in the right knee. It is appropriate when the laterality and organism are both stated in the record. If the organism is not confirmed, check documentation before assigning M00.161.
Do not use for
Do not use this code for arthritis in another joint, unspecified knee laterality, or noninfectious joint inflammation. It also should not be used when pneumococcal infection is documented elsewhere without knee joint involvement.
Coding tip
Verify both the causative organism and right-knee laterality in the provider note before coding.