Pyogenic knee arthritis caused by group A β-hemolytic Streptococcus: a toxic shock-prevented case.

Pyogenic knee arthritis caused by group A β-hemolytic Streptococcus (GAS) is rare. GAS sometimes causes group A β-hemolytic streptococcal toxic shock syndrome. We encountered a case of pyogenic knee arthritis caused by GAS that resolved after appropriate treatment (emergency arthroscopic synovectomy and medication) administered within 48 h of onset. In cases of a history of another infection with acute knee joint pain, the possibility of GAS-induced pyogenic knee arthritis should be considered, and proper treatment should be administered immediately.