Acute traumatic knee hemarthrosis.

A rapidly developing hemarthrosis in an acutely injured knee is reported to be associated with "surgically significant" lesions, such as anterior cruciate ligament tears, meniscus tears, and osteochondral fractures, in < or = 90% of cases. We report two cases of adult men who showed signs of such acute hemarthroses in stable knees after significant trauma. Neither had significant intraarticular pathology, such as meniscal, articular, or ligamentous injury, at arthroscopy. Persistent postarthroscopic bleeding led to additional diagnostic testing that found mild factor VIII deficiency. Hemophilia A and other clotting disorders should be considered by arthroscopic surgeons as a possible cause of a posttraumatic hemarthrosis.