Spontaneous Recurrent Hemarthrosis of the Knee: A Report of Two Cases with a Source of Bleeding Detected during Arthroscopic Surgery of the Knee Joint.

We report two cases of the spontaneous recurrent hemarthrosis of the knee. In these cases lateral meniscus was severely torn and a small tubular soft tissue with pulsation was identified on the synovium in the posterolateral corner during arthroscopic surgery of the knee joint. Gentle grasping of this tissue by forceps led to pulsating bleeding, which stopped by electrocoagulation. This soft tissue was considered a source of bleeding, since no recurrence of hemarthrosis was observed for more than four years after surgery. It was highly probable that this soft tissue was the ruptured end of the lateral inferior genicular artery or its branch. This case report strongly supports the theory that the bleeding from the peripheral arteries of the posterior portion of the lateral meniscus is the cause of spontaneous recurrent hemarthrosis of the knee.