AbstractSpontaneous knee dislocation without a history of trauma is a rare entity to witness. Herein, we report a case of a patient who presented to the emergency department (ED) with a history of fever, chills and vomiting associated with progressive right knee swelling, pain and impaired range of motion (ROM). Physical exam of her right knee showed symmetrical swelling with diffuse tenderness and limited ROM due to pain. Joint aspirate and full septic workup confirmed the diagnosis of septic arthritis. Following her management and two events of irrigation and debridement of the septic knee, the patient was discharged. However, after 1-week from discharge, she presented to ED with right leg swelling and tenderness despite being bedbound for 3 months and denying any history of trauma with radiographs showing a posterior knee dislocation. This report aimed to shed a light on this dreadful complication of septic arthritis and highlights the importance of early recognition and management.