Four patients with hemarthrosis of the knee, synovial rupture, and ecchymoses are reported. The patients presented with calf pain and swelling and large ecchymoses, which eventually extended to the ankle as a crescent about one or both malleoli. Appreciation of this physical sign, which appears to be characteristic for the hemorrhagic subset of synovial rupture, should alert the physician to the correct diagnosis and steer him away from contraindicated anticoagulant therapy.