Septic arthritis is inflammation of the joints secondary to an infectious etiology such as bacterial, fungal, mycobacterial, viral, or other pathogens. It is usually monoarticular, however, polyarticular septic arthritis involving many or smaller joints may also occur.

If a post-procedural infection results in septic shock, the ICD-10-CM Chapter 1 Guidelines instructs to first code the sepsis due to postprocedural infection (see codes above), followed by code T81.12-, Postprocedural septic shock. The guidelines state not to assign code R65.21, Severe sepsis with septic shock.