Clopidogrel-induced hemarthrosis following knee replacement

: Background Clopidogrel is an adenosine diphosphate receptor antagonist used in patients with atherosclerotic vascular disease to reduce the incidence of ischemic events. Case Presentation A 62-year-old woman developed a spontaneous hemarthrosis of her left knee following clopidogrel treatment. To date, no case of spontaneous hemarthrosis following clopidogrel monotherapy was reported. Prompt aspiration after discontinuing clopidogrel by conservative management can assist early diagnosis and prevent further damage to the joint. The assessment of the causality of the event was carried out via Naranjo Causality Assessment Scale. A score of 5 was reported for this patient, indicating clopidogrel as a probable cause of this reaction. Conclusion We conclude that spontaneous hemarthrosis is a possible complication following clopidogrel therapy and it needs assessment when appropriate clinical symptoms (e.g. intra-articular effusion, pain) are present.