Acute septic arthritis of the knee: A rare case report of infection with Parvimonas micra after an intra-articular corticosteroid injection for osteoarthritis

Acute bacterial mono-articular septic arthritis affects most commonly the lower extremity joints in adult population and most commonly caused by Staphylococcus aureus. Various risk factors determine susceptibility to infection including host immunity, medical co-morbidity and joint structural abnormality and other organisms may be involved. Parvimonas micra (P. micra) is among the rare organisms that may be associated with atypical septic arthritis and primarily affects the native knee joint. Only 3 case reports in the literature have reported on pyogenic pyogenic joint infection caused by this organism. We hereby present our experience with a case of knee septic arthritis caused by P. micra in a patient with knee osteoarthritis following a recent intra-articular injection with corticosteroids. In susceptible patients, Intra-articular corticosteroid injection and crystal induced arthritis may propose a potential risk of contracting infection with P. micra.